FinnAPL idiom library

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The FinnAPL idiom library contains a collection of over 700 one-line APL idioms to accomplish a large variety of tasks. It was first presented at the 1984 APL conference in Helsinki, Finland. The huge contribution of the Finnish APL Association is gratefully acknowledged.

The original FinnAPL idiom library

This listing mainly suffers from two issues:

  • Due to its age, it doesn't make use of modern APL features which can provide a simpler solution. (However, a simple-looking expression which uses nested arrays might be far more computationally expensive than a longer, more involved solution which only uses simple arrays.)
  • It can be hard to find what one is looking for, both because computing terminology has changed, and because pinpointing the exact term can be difficult.

APLcart includes all of the below library, updated to use the latest language features, and in an easily searchable format that includes modern day synonyms.

Interpreting an entry in the Idiom Library

As an example of how each entry in the library is arranged, consider the first idiom:

1. Progressive index of (without replacement) <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>((⍴X)⍴⍋⍋X⍳X,Y)⍳(⍴Y)⍴⍋⍋X⍳Y,X</source>

The entry includes a brief description of what the idiom does, which is followed by the expression <syntaxhighlight lang=apl inline>X←A1; Y←A1</source> which specifies the types and ranks of the arguments:

<syntaxhighlight lang=apl inline>A</source> Any [Numeric, Character or Boolean]
<syntaxhighlight lang=apl inline>D</source> Numeric
<syntaxhighlight lang=apl inline>I</source> Integer
<syntaxhighlight lang=apl inline>C</source> Character
<syntaxhighlight lang=apl inline>B</source> Boolean

A number following the type indicates the rank, e.g.

<syntaxhighlight lang=apl inline>A0</source> Any scalar (rank 0)
<syntaxhighlight lang=apl inline>A1</source> Any vector (rank 1)
<syntaxhighlight lang=apl inline>A2</source> Any matrix (rank 2)

Thus the idiom shown expects two character or numeric vectors, <syntaxhighlight lang=apl inline>X</source> and <syntaxhighlight lang=apl inline>Y</source>. It will find the index position of each element of <syntaxhighlight lang=apl inline>Y</source> in <syntaxhighlight lang=apl inline>X</source>, for example:

<syntaxhighlight lang=apl>

     X←'which side does an ostrich have its feathers?'
     Y←'on the outside, of course!'
     ((⍴X)⍴⍋⍋X⍳X,Y)⍳(⍴Y)⍴⍋⍋X⍳Y,X

13 18 6 22 2 10 11 20 46 34 7 3 9 14 46 16 46 37 19 4 46 46 23 15 31 46

     (X,'-')[((⍴X)⍴⍋⍋X⍳X,Y)⍳(⍴Y)⍴⍋⍋X⍳Y,X]

on the o-tside- -f c--rse- </source>

In this example, the first 'o' character in <syntaxhighlight lang=apl inline>Y</source> occurs in at index position 13 in <syntaxhighlight lang=apl inline>X</source>, the second one occurs at position 20, and the third and fourth 'o' characters are not present in <syntaxhighlight lang=apl inline>X</source>.

For a more detailed description of how this particular idiom works, see this analysis by Bob Smith.

Idiom Library Listing

Grade Up <syntaxhighlight lang=apl inline>⍋</source>

1. Progressive index of (without replacement) <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>((⍴X)⍴⍋⍋X⍳X,Y)⍳(⍴Y)⍴⍋⍋X⍳Y,X</source>
2. Ascending cardinal numbers (ranking, shareable) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⌊.5×(⍋⍋X)+⌽⍋⍋⌽X</source>
3. Cumulative maxima (<syntaxhighlight lang=apl inline>⌈\</source>) of subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[A⍳⌈\A←⍋A[⍋(+\X)[A←⍋Y]]]</source>
4. Cumulative minima (<syntaxhighlight lang=apl inline>⌊\</source>) of subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[A⍳⌈\A←⍋A[⍋(+\X)[A←⍒Y]]]</source>
5. Progressive index of (without replacement) <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>((⍋X⍳X,Y)⍳⍳⍴X)⍳(⍋X⍳Y,X)⍳⍳⍴Y</source>
6. Test if X and Y are permutations of each other <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[⍋Y]∧.=X[⍋X]</source>
7. Test if X is a permutation vector <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X∧.=⍋⍋X</source>
8. Grade up (<syntaxhighlight lang=apl inline>⍋</source>) for sorting subvectors of Y having lengths X <syntaxhighlight lang=apl inline>Y←D1; X←I1; (⍴Y) ←→ +/X</source>
<syntaxhighlight lang=apl inline>A[⍋(+\(⍳⍴Y)∊+\⎕IO,X)[A←⍋Y]]</source>
9. Index of the elements of X in Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>(((1,A)/B)⌊1+⍴Y)[(⍴Y)↓(+\1,A←(1↓A)≠¯1↓A←A[B])[⍋B←⍋A←Y,X]]</source>
10. Minima (⌊/) of elements of subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[A[X/⍋(+\X)[A←⍋Y]]]</source>
11. Grade up (<syntaxhighlight lang=apl inline>⍋</source>) for sorting subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>A[⍋(+\X)[A←⍋Y]]</source>
12. Occurences of the elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>|-⌿(2,⍴X)⍴⍋⍋X,X</source>
13. Sorting rows of matrix X into ascending order <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>(⍴X)⍴(,X)[A[⍋(,⍉(⌽⍴X)⍴⍳1↑⍴X)[A←⍋,X]]]</source>
14. Adding a new dimension after dimension G Y-fold <syntaxhighlight lang=apl inline>G←I0; Y←I0; X←A</source>
<syntaxhighlight lang=apl inline>(⍋⍋(G+1),⍳⍴⍴X)⍉(Y,⍴X)⍴X</source>
15. Sorting rows of matrix X into ascending order <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>A←(⍋,X)-⎕IO ⋄ (⍴X)⍴(,X)[⎕IO+A[⍋⌊A÷¯1↑⍴X]]</source>
16. Y smallest elements of X in order of occurrence <syntaxhighlight lang=apl inline>X←D1, Y←I0</source>
<syntaxhighlight lang=apl inline>((⍋⍋X)∊⍳Y)/X</source>
17. Merging X, Y, Z ... under control of G (mesh) <syntaxhighlight lang=apl inline>X←A1; Y←A1; Z←A1; ... ; G←I1</source>
<syntaxhighlight lang=apl inline>(X,Y,Z,...)[⍋⍋G]</source>
18. Merging X and Y under control of G (mesh) <syntaxhighlight lang=apl inline>X←A1; Y←A1; G←B1</source>
<syntaxhighlight lang=apl inline>(X,Y)[⍋⍋G]</source>
19. Ascending cardinal numbers (ranking, all different) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⍋⍋X</source>
20. Grade down (<syntaxhighlight lang=apl inline>⍒</source>) for sorting subvectors of Y having lengths X <syntaxhighlight lang=apl inline>Y←D1; X←I1; (⍴Y) ←→ +/X</source>
<syntaxhighlight lang=apl inline>A[⍋(+\(⍳⍴Y)∊+\⎕IO,X)[A←⍒Y]]</source>
21. Maxima (⌈/) of elements of subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[A[X/⍋(+\X)[A←⍒Y]]]</source>
22. Grade down (<syntaxhighlight lang=apl inline>⍒</source>) for sorting subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>A[⍋(+\X)[A←⍒Y]]</source>
23. Y largest elements of X in order of occurrence <syntaxhighlight lang=apl inline>X←D1; Y←I0</source>
<syntaxhighlight lang=apl inline>((⍋⍒X)∊⍳Y)/X</source>
24. Merging X and Y under control of G (mesh) <syntaxhighlight lang=apl inline>X←A1; Y←A1; G←B1</source>
<syntaxhighlight lang=apl inline>(Y,X)[⍋⍒G]</source>
25. Descending cardinal numbers (ranking, all different) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⍋⍒X</source>
26. Sorting rows of X according to key Y (alphabetizing) <syntaxhighlight lang=apl inline>X←A2; Y←A1</source>
<syntaxhighlight lang=apl inline>X[⍋(1+⍴Y)⊥Y⍳⍉X;]</source>
27. Diagonal ravel <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>(,X)[⍋+⌿(⍴X)⊤(⍳⍴,X)-⎕IO]</source>
28. Grade up according to key Y <syntaxhighlight lang=apl inline>Y←A1; X←A1</source>
<syntaxhighlight lang=apl inline>⍋Y⍳X</source>
29. Test if X is a permutation vector <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X[⍋X]∧.=⍳⍴X</source>
30. Sorting a matrix into lexicographic order <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>X[⍋+⌿A<.-⍉A←X,0;]</source>
31. Sorting words in list X according to word length <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>X[⍋X+.≠' ';]</source>
32. Classification of X to classes starting with Y <syntaxhighlight lang=apl inline>X←D1;Y←D1;Y<.≥1⌽Y</source>
<syntaxhighlight lang=apl inline>A[(B/C)-⍴Y]←B/+\~B←(⍴Y)<C←⍋Y,X+A←0×X ⋄ A</source>
33. Rotate first elements (<syntaxhighlight lang=apl inline>1⌽</source>) of subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←A1</source>
<syntaxhighlight lang=apl inline>Y[⍋X++\X]</source>
34. Doubling quotes (for execution) <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(X,')[(⎕IO+⍴X)⌊⍋(⍳⍴X),('=X)/⍳⍴X]</source>
35. Inserting Y <syntaxhighlight lang=apl inline>*</source>'s into vector X after indices G <syntaxhighlight lang=apl inline>X←C1; Y←I0; G←I1</source>
<syntaxhighlight lang=apl inline>(X,'*')[(⎕IO+⍴X)⌊⍋(⍳⍴X),(Y×⍴G)⍴G]</source>
36. Median[1] <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X[(⍋X)[⌈.5×⍴X]]</source>
37. Index of last maximum element of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>¯1↑⍋X</source>
38. Index of (first) minimum element of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>1↑⍋X</source>
39. Expansion vector with zero after indices Y <syntaxhighlight lang=apl inline>X←D1; Y←I1</source>
<syntaxhighlight lang=apl inline>(⍴X)≥⍋(⍳⍴X),Y</source>
40. Catenating G elements H before indices Y in vector X <syntaxhighlight lang=apl inline>X←A1; Y←I1; G←I0; H←A0</source>
<syntaxhighlight lang=apl inline>A←G×⍴,Y ⋄ ((A⍴H),X)[⍋(A⍴Y),⍳⍴X]</source>
41. Catenating G elements H after indices Y in vector X <syntaxhighlight lang=apl inline>X←A1; Y←I1; G←I0; H←A0</source>
<syntaxhighlight lang=apl inline>A←G×⍴,Y ⋄ (X,A⍴H)[⍋(⍳⍴X),A⍴Y]</source>
42. Merging X and Y under control of G (mesh) <syntaxhighlight lang=apl inline>X←A1; Y←A1; G←B1</source>
<syntaxhighlight lang=apl inline>A[⍋G]←A←Y,X ⋄ A</source>
43. Sorting a matrix according to Y:th column <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>X[⍋X[;Y];]</source>
44. Sorting indices X according to data Y <syntaxhighlight lang=apl inline>X←I1; Y←D1</source>
<syntaxhighlight lang=apl inline>X[⍋Y[X]]</source>
45. Choosing sorting direction during execution <syntaxhighlight lang=apl inline>X←D1; Y←I0</source>
<syntaxhighlight lang=apl inline>⍋X×(¯1 1)[Y]</source>
46. Sorting Y according to X <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>Y[⍋X]</source>
47. Sorting X into ascending order <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X[⍋X]</source>
48. Inverting a permutation <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>⍋X</source>

Grade Down <syntaxhighlight lang=apl inline>⍒</source>

49. Reverse vector X on condition Y <syntaxhighlight lang=apl inline>X←A1; Y←B0</source>
<syntaxhighlight lang=apl inline>X[⍒Y!⍳⍴X]</source>
50. Sorting a matrix into reverse lexicographic order <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>X[⍒+⌿A<.-⍉A←X,0;]</source>
52. Reversal (<syntaxhighlight lang=apl inline>⌽</source>) of subvectors of X having lengths Y <syntaxhighlight lang=apl inline>X←D1; Y←I1</source>
<syntaxhighlight lang=apl inline>X[⌽⍒+\(⍳⍴X)∊+\⎕IO,Y]</source>
53. Reversal (<syntaxhighlight lang=apl inline>⌽</source>) of subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←A1</source>
<syntaxhighlight lang=apl inline>Y[⌽⍒+\X]</source>
55. Indices of ones in logical vector X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>(+/X)↑⍒X</source>
56. Index of first maximum element of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>1↑⍒X</source>
57. Moving all blanks to end of text <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>X[⍒' '≠X]</source>
58. Sorting X into descending order <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X[⍒X]</source>
59. Moving elements satisfying condition Y to the start of X <syntaxhighlight lang=apl inline>X←A1; Y←B1</source>
<syntaxhighlight lang=apl inline>X[⍒Y]</source>

Matrix Inversion / Matrix Division <syntaxhighlight lang=apl inline>⌹</source>

60. Interpolated value of series (X,Y) at G <syntaxhighlight lang=apl inline>X←D1; Y←D1; G←D0</source>
<syntaxhighlight lang=apl inline>G⊥Y⌹X∘.*⌽-⎕IO-⍳⍴X</source>
61. Predicted values of exponential (curve) fit <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>*A+.×(⍟Y)⌹A←X∘.*0 1</source>
62. Coefficients of exponential (curve) fit of points (X,Y) <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>A←(⍟Y)⌹X∘.*0 1 ⋄ A[1]←*A[1] ⋄ A</source>
63. Predicted values of best linear fit (least squares) <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>A+.×Y⌹A←X∘.*0 1</source>
64. G-degree polynomial (curve) fit of points (X,Y) <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>⌽Y⌹X∘.*0,⍳G</source>
65. Best linear fit of points (X,Y) (least squares) <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y⌹X∘.*0 1</source>

Decode <syntaxhighlight lang=apl inline>⊥</source>

66. Binary format of decimal number X <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>⍕10⊥((1+⌈2⍟⌈/,X)⍴2)⊤X</source>
67. Barchart of two integer series (across the page) <syntaxhighlight lang=apl inline>X←I2; 1⍴⍴X ←→ 2</source>
<syntaxhighlight lang=apl inline>' *○⍟'[⎕IO+2⊥X∘.≥⍳⌈/,X]</source>
68. Case structure with an encoded branch destination <syntaxhighlight lang=apl inline>Y←I1; X←B1</source>
<syntaxhighlight lang=apl inline>→Y[1+2⊥X]</source>
69. Representation of current time (24 hour clock) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>A←⍕1000⊥3↑3↓⎕TS ⋄ A[3 6]←':' ⋄ A</source>
70. Representation of current date (descending format) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>A←⍕1000⊥3↑⎕TS ⋄ A[5 8]←'-' ⋄ A</source>
71. Representation of current time (12 hour clock) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>(1⌽,' ::',3 2⍴6 0⍕100⊥12 0 0|3↑3↓⎕TS),'AP'[1+12≤⎕TS[4]],'M'</source>
73. Removing duplicate rows <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>((A⍳A)=⍳⍴A←2⊥X∧.=⍉X)⌿X</source>
74. Conversion from hexadecimal to decimal <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>16⊥-⎕IO-'0123456789ABCDEF'⍳⍉X</source>
75. Conversion of alphanumeric string into numeric <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>10⊥¯1+'0123456789'⍳X</source>
76. Value of polynomial with coefficients Y at points X <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>(X∘.+,0)⊥Y</source>
77. Changing connectivity list X to a connectivity matrix <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>A←(×/B←0 0+⌈/,X)⍴0 ⋄ A[⎕IO+B[1]⊥-⎕IO-X]←1 ⋄ B⍴A</source>
78. Present value of cash flows X at interest rate Y % <syntaxhighlight lang=apl inline>X←D1; Y←D0</source>
<syntaxhighlight lang=apl inline>(÷1+Y÷100)⊥⌽X</source>
79. Justifying right <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(1-(' '=X)⊥1)⌽X</source>
80. Number of days in month X of years Y (for all leap years) <syntaxhighlight lang=apl inline>X←I0; Y←I</source>
<syntaxhighlight lang=apl inline>(12⍴7⍴31 30)[X]-0⌈¯1+2⊥(X=2),[.1](0≠400|Y)-(0≠100|Y)-0≠4|Y</source>
81. Number of days in month X of years Y (for most leap years) <syntaxhighlight lang=apl inline>X←I0; Y←I</source>
<syntaxhighlight lang=apl inline>(12⍴7⍴31 30)[X]-0⌈¯1+2⊥(X=2),[.1]0≠4|Y</source>
82. Encoding current date <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>100⊥100|3↑⎕TS</source>
83. Removing trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(1-(' '=X)⊥1)↓X</source>
84. Index of first non-blank, counted from the rear <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(' '=X)⊥1</source>
85. Indexing scattered elements <syntaxhighlight lang=apl inline>X←A; Y←I2</source>
<syntaxhighlight lang=apl inline>(,X)[⎕IO+(⍴X)⊥Y-⎕IO]</source>
86. Conversion of indices Y of array X to indices of raveled X <syntaxhighlight lang=apl inline>X←A; Y←I2</source>
<syntaxhighlight lang=apl inline>⎕IO+(⍴X)⊥Y-⎕IO</source>
87. Number of columns in array X as a scalar <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>0⊥⍴X</source>
88. Future value of cash flows X at interest rate Y % <syntaxhighlight lang=apl inline>X←D1; Y←D0</source>
<syntaxhighlight lang=apl inline>(1+Y÷100)⊥X</source>
89. Sum of the elements of vector X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>1⊥X</source>
90. Last element of numeric vector X as a scalar <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>0⊥X</source>
91. Last row of matrix X as a vector <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>0⊥X</source>
92. Integer representation of logical vectors <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>2⊥X</source>
93. Value of polynomial with coefficients Y at point X <syntaxhighlight lang=apl inline>X←D0; Y←D</source>
<syntaxhighlight lang=apl inline>X⊥Y</source>

Encode <syntaxhighlight lang=apl inline>⊤</source>

94. Conversion from decimal to hexadecimal (<syntaxhighlight lang=apl inline>X=1..255</source>) <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>⍉'0123456789ABCDEF'[⎕IO+((⌈⌈/16⍟,X)⍴16)⊤X]</source>
this alternative opens the range to 0..⌊/⍳0
<syntaxhighlight lang=apl inline>⍉'0123456789ABCDEF'[⎕IO+((1+⌊16⍟⌈/X+X=0)⍴16)⊤X]</source>
95. All binary representations up to X (truth table) <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>((⌈2⍟1+X)⍴2)⊤0,⍳X</source>
96. Representation of X in base Y <syntaxhighlight lang=apl inline>X←D0; Y←D0</source>
<syntaxhighlight lang=apl inline>((1+⌊Y⍟X)⍴Y)⊤X</source>
97. Digits of X separately <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>((1+⌊10⍟X)⍴10)⊤X</source>
98. Helps locating column positions 1..X <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>1 0⍕10 10⊤1-⎕IO-⍳X</source>
99. Conversion of characters to hexadecimal representation (<syntaxhighlight lang=apl inline>⎕AV</source>) <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>,' ',⍉'0123456789ABCDEF'[⎕IO+16 16⊤-⎕IO-⎕AV⍳X]</source>
100. Polynomial with roots X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⌽((0,⍳⍴X)∘.=+⌿~A)+.×(-X)×.*A←((⍴X)⍴2)⊤¯1+⍳2*⍴X</source>
101. Index pairs of saddle points <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>⎕IO+(⍴X)⊤-⎕IO-(,(X=(⍴X)⍴⌈⌿X)∧X=⍉(⌽⍴X)⍴⌊/X)/⍳×/⍴X</source>
102. Changing connectivity matrix X to a connectivity list <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(,X)/1+A⊤¯1+⍳×/A←⍴X</source>
103. Matrix of all indices of X <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⎕IO+(⍴X)⊤(⍳×/⍴X)-⎕IO</source>
104. Separating a date YYMMDD to YY, MM, DD <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>⍉(3⍴100)⊤X</source>
105. Indices of elements Y in array X <syntaxhighlight lang=apl inline>X←A; Y←A</source>
<syntaxhighlight lang=apl inline>⎕IO+(⍴X)⊤(-⎕IO)+(,X∊Y)/⍳⍴,X</source>
106. All pairs of elements of <syntaxhighlight lang=apl inline>⍳X</source> and <syntaxhighlight lang=apl inline>⍳Y</source> <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>⎕IO+(X,Y)⊤(⍳X×Y)-⎕IO</source>
107. Matrix for choosing all subsets of X (truth table) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>((⍴X)⍴2)⊤¯1+⍳2*⍴X</source>
108. All binary representations with X bits (truth table) <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(X⍴2)⊤¯1+⍳2*X</source>
109. Incrementing cyclic counter X with upper limit Y <syntaxhighlight lang=apl inline>X←D; Y←D0</source>
<syntaxhighlight lang=apl inline>1+Y⊤X</source>
110. Decoding numeric code ABBCCC into a matrix <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>10 100 1000⊤X</source>
111. Integer and fractional parts of positive numbers <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>0 1⊤X</source>

Logarithm <syntaxhighlight lang=apl inline>⍟</source>

112. Number of decimals of elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⌊10⍟(⍎('.'≠A)/A←⍕X)÷X</source>
113. Number of sortable columns at a time using <syntaxhighlight lang=apl inline>⊥</source> and alphabet X <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>⌊(1+⍴X)⍟2*(A=¯1+A←2*⍳128)⍳1</source>
114. Playing order in a cup for X ranked players <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>,⍉(A⍴2)⍴(2*A←⌈2⍟X)↑⍳X</source>
115. Arithmetic precision of the system (in decimals) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⌊|10⍟|1-3×÷3</source>
116. Number of digitpositions in integers in X <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>1+(X<0)+⌊10⍟|X+0=X</source>
117. Number of digit positions in integers in X <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>1+⌊10⍟(X=0)+X×(1 ¯10)[1+X<0]</source>
118. Number of digits in positive integers in X <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>1+⌊10⍟X+0=X</source>

Branch <syntaxhighlight lang=apl inline>→</source>

119. Case structure according to key vector G <syntaxhighlight lang=apl inline>X←A0; Y←I1; G←A1</source>
<syntaxhighlight lang=apl inline>→Y[G⍳X]</source>
120. Forming a transitive closure <syntaxhighlight lang=apl inline>X←B2</source>
<syntaxhighlight lang=apl inline>→⎕LC⌈⍳∨/,(X←X∨X∨.∧X)≠+X</source>
121. Case structure with integer switch <syntaxhighlight lang=apl inline>X←I0; Y←I1</source>
<syntaxhighlight lang=apl inline>→X⌽Y</source>
122. For-loop ending construct <syntaxhighlight lang=apl inline>X←I0; Y←I0; G←I0</source>
<syntaxhighlight lang=apl inline>→Y⌈⍳G≥X←X+1</source>
123. Conditional branch to line Y <syntaxhighlight lang=apl inline>X←B0; Y←I0; Y>0</source>
<syntaxhighlight lang=apl inline>→Y⌈⍳X</source>
124. Conditional branch out of program <syntaxhighlight lang=apl inline>X←B0</source>
<syntaxhighlight lang=apl inline>→0⌊⍳X</source>
125. Conditional branch depending on sign of X <syntaxhighlight lang=apl inline>X←I0; Y←I1</source>
<syntaxhighlight lang=apl inline>→Y[2+×X]</source>
126. Continuing from line Y (if X>0) or exit <syntaxhighlight lang=apl inline>X←D0; Y←I0</source>
<syntaxhighlight lang=apl inline>→Y××X</source>
127. Case structure using levels with limits G <syntaxhighlight lang=apl inline>X←D0; G←D1; Y←I1</source>
<syntaxhighlight lang=apl inline>→(X≥G)/Y</source>
128. Case structure with logical switch (preferring from start) <syntaxhighlight lang=apl inline>X←B1; Y←I1</source>
<syntaxhighlight lang=apl inline>→X/Y</source>
129. Conditional branch out of program <syntaxhighlight lang=apl inline>X←B0</source>
<syntaxhighlight lang=apl inline>→0×⍳X</source>

Execute <syntaxhighlight lang=apl inline>⍎</source>

132. Test for symmetricity of matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>⍎⍎'1','↑↓'[⎕IO+∧/(⍴X)=⌽⍴X],0~0∊X=⍉X</source>
133. Using a variable named according to X <syntaxhighlight lang=apl inline>X←A0; Y←A</source>
<syntaxhighlight lang=apl inline>⍎'VAR',(⍕X),'←Y'</source>
134. Rounding to <syntaxhighlight lang=apl inline>⎕PP</source> precision <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⍎⍕X</source>
135. Convert character or numeric data into numeric <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>⍎⍕X</source>
136. Reshaping only one-element numeric vector X into a scalar <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⍎⍕X</source>
137. Graph of F(X) at points X ('X'∊F) <syntaxhighlight lang=apl inline>F←A1; X←D1</source>
<syntaxhighlight lang=apl inline>' *'[⎕IO+(⌽(¯1+⌊/A)+⍳1+(⌈/A)-⌊/A)∘.=A←⌊.5+⍎F]</source>
138. Conversion of each row to a number (default zero) <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(X∨.≠' ')\1↓⍎'0 ',,X,' '</source>
139. Test for symmetricity of matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>⍎(¯7*A∧.=⌽A←⍴X)↑'0~0∊X=⍉X'</source>
140. Execution of expression X with default value Y <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⍎((X∧.=' ')/'Y'),X</source>
141. Changing X if a new input value is given <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>X←⍎,((2↑'X'),' ',[.5]A)[⎕IO+~' '∧.=A←⍞;]</source>
142. Definite integral of F(X) in range Y with G steps ('X'∊F) <syntaxhighlight lang=apl inline>F←A1; G←D0; Y←D1; ⍴Y ←→ 2</source>
<syntaxhighlight lang=apl inline>A+.×⍎F,0⍴X←Y[1]+(A←--/Y÷G)×0,⍳G</source>
143. Test if numeric and conversion to numeric form <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>1↓⍎'0 ',(∧/X∊' 0123456789')/X</source>
144. Tests the social security number (Finnish) <syntaxhighlight lang=apl inline>Y←'01...9ABC...Z'; 10=⍴X</source>
<syntaxhighlight lang=apl inline>(¯1↑X)=((~Y∊'GIOQ')/Y)[1+31|⍎9↑X]</source>
145. Conditional execution <syntaxhighlight lang=apl inline>X←B0</source>
<syntaxhighlight lang=apl inline>⍎X/'EXPRESSION'</source>
146. Conditional branch out of programs <syntaxhighlight lang=apl inline>X←B0</source>
<syntaxhighlight lang=apl inline>⍎X/'→'</source>
147. Using default value 100 if X does not exist <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⍎(¯3*2≠⎕NC 'X')↑'X100'</source>
148. Conditional execution <syntaxhighlight lang=apl inline>X←B0</source>
<syntaxhighlight lang=apl inline>⍎X↓'⍝ ...'</source>
149. Giving a numeric default value for input <syntaxhighlight lang=apl inline>X←D0</source>
<syntaxhighlight lang=apl inline>1⍴(⍎⍞,',⍳0'),X</source>
150. Assign values of expressions in X to variables named in Y <syntaxhighlight lang=apl inline>X←C2; Y←C2</source>
<syntaxhighlight lang=apl inline>A←⍎,',','(','0','⍴',Y,'←',X,')'</source>
151. Evaluation of several expressions; results form a vector <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⍎,',','(',',',X,')'</source>
152. Sum of numbers in character matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>⍎,'+',X</source>
153. Indexing when rank is not known beforehand <syntaxhighlight lang=apl inline>X←A; Y←I</source>
<syntaxhighlight lang=apl inline>⍎'X[',((¯1+⍴⍴X)⍴';'),'Y]'</source>

Format <syntaxhighlight lang=apl inline>⍕</source>

154. Numeric headers (elements of X) for rows of table Y <syntaxhighlight lang=apl inline>X←D1; Y←A2</source>
<syntaxhighlight lang=apl inline>(3⌽7 0⍕X∘.+,0),⍕Y</source>
155. Formatting a numerical vector to run down the page <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⍕X∘.+,0</source>
156. Representation of current date (ascending format) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>A←⍕⌽3↑⎕TS ⋄ A[(' '=A)/⍳⍴A]←'.' ⋄ A</source>
157. Representation of current date (American) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>A←⍕100|1⌽3↑⎕TS ⋄ A[(' '=A)/⍳⍴A]←'/' ⋄ A</source>
158. Formatting with zero values replaced with blanks <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>(⍴A)⍴B\(B←,('0'≠A)∨' '≠¯1⌽A)/,A←' ',⍕X</source>
159. Number of digit positions in scalar X (depends on <syntaxhighlight lang=apl inline>⎕PP</source>) <syntaxhighlight lang=apl inline>X←D0</source>
<syntaxhighlight lang=apl inline>⍴⍕X</source>
160. Leading zeroes for X in fields of width Y <syntaxhighlight lang=apl inline>X←I1; Y←I0; X≥0</source>
<syntaxhighlight lang=apl inline>0 1↓(2↑Y+1)⍕X∘.+,10*Y</source>
161. Row-by-row formatting (width G) of X with Y decimals per row <syntaxhighlight lang=apl inline>X←D2; Y←I1; G←I0</source>
<syntaxhighlight lang=apl inline>((1,G)×⍴X)⍴2 1 3⍉(⌽G,⍴X)⍴(,G,[1.1]Y)⍕⍉X</source>
163. Formatting X with H decimals in fields of width G <syntaxhighlight lang=apl inline>X←D; G←I1; H←I1</source>
<syntaxhighlight lang=apl inline>(,G,[1.1]H)⍕X</source>

Roll / Deal <syntaxhighlight lang=apl inline>?</source>

164. Y-shaped array of random numbers within ( X[1],X[2] ] <syntaxhighlight lang=apl inline>X←I1; Y←I1</source>
<syntaxhighlight lang=apl inline>X[1]+?Y⍴--/X</source>
165. Removing punctuation characters <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(~X∊' .,:;?)/X</source>
166. Choosing Y objects out of <syntaxhighlight lang=apl inline>⍳X</source> with replacement (roll) <syntaxhighlight lang=apl inline>Y←I; X←I</source>
<syntaxhighlight lang=apl inline>?Y⍴X</source>
167. Choosing Y objects out of <syntaxhighlight lang=apl inline>⍳X</source> without replacement (deal) <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>Y?X</source>

Geometrical Functions <syntaxhighlight lang=apl inline>○</source>

168. Arctan Y÷X <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>((X≠0)ׯ3○Y÷X+X=0)+○((X=0)×.5××Y)+(X<0)×1-2×Y<0</source>
169. Conversion from degrees to radians <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X×○÷180</source>
170. Conversion from radians to degrees <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X×180÷○1</source>
171. Rotation matrix for angle X (in radians) counter-clockwise <syntaxhighlight lang=apl inline>X←D0</source>
<syntaxhighlight lang=apl inline>2 2⍴1 ¯1 1 1×2 1 1 2○X</source>

Factorial / Binomial <syntaxhighlight lang=apl inline>!</source>

172. Number of permutations of X objects taken Y at a time <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>(!Y)×Y!X</source>
173. Value of Taylor series with coefficients Y at point X <syntaxhighlight lang=apl inline>X←D0; Y←D1</source>
<syntaxhighlight lang=apl inline>+/Y×(X*A)÷!A←¯1+⍳⍴Y</source>
174. Poisson distribution of states X with average number Y <syntaxhighlight lang=apl inline>X←I; Y←D0</source>
<syntaxhighlight lang=apl inline>(*-Y)×(Y*X)÷!X</source>
175. Gamma function <syntaxhighlight lang=apl inline>X←D0</source>
<syntaxhighlight lang=apl inline>!X-1</source>
176. Binomial distribution of X trials with probability Y <syntaxhighlight lang=apl inline>X←I0; Y←D0</source>
<syntaxhighlight lang=apl inline>(A!X)×(Y*A)×(1-Y)*X-A←-⎕IO-⍳X+1</source>
177. Beta function <syntaxhighlight lang=apl inline>X←D0; Y←D0</source>
<syntaxhighlight lang=apl inline>÷Y×(X-1)!Y+X-1</source>
178. Selecting elements satisfying condition X, others to 1 <syntaxhighlight lang=apl inline>X←B; Y←D</source>
<syntaxhighlight lang=apl inline>X!Y</source>
179. Number of combinations of X objects taken Y at a time <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>Y!X</source>

Index Of <syntaxhighlight lang=apl inline>⍳</source>

180. Removing elements Y from beginning and end of vector X <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>((A⍳1)-⎕IO)↓(⎕IO-(⌽A←~X∊Y)⍳1)↓X</source>
181. Alphabetical comparison with alphabets G <syntaxhighlight lang=apl inline>X←A; Y←A</source>
<syntaxhighlight lang=apl inline>(G⍳X)<G⍳Y</source>
183. Sum over elements of X determined by elements of Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>X+.×Y∘.=((⍳⍴Y)=Y⍳Y)/Y</source>
184. First occurrence of string X in string Y <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>(∧⌿(¯1+⍳⍴X)⌽X∘.=Y)⍳1</source>
185. Removing duplicate rows <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>((A⍳A)=⍳⍴A←⎕IO++⌿∧⍀X∨.≠⍉X)⌿X</source>
186. First occurrence of string X in matrix Y <syntaxhighlight lang=apl inline>X←A1; Y←A2; ¯1↑⍴Y←→⍴X</source>
<syntaxhighlight lang=apl inline>(Y∧.=X)⍳1</source>
187. Indices of ones in logical vector X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>(+\X)⍳⍳+/X</source>
188. Executing costly monadic function F on repetitive arguments <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(F B/X)[+\B←(X⍳X)=⍳⍴X]</source>
189. Index of (first) maximum element of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X⍳⌈/X</source>
190. Index of first occurrence of elements of Y <syntaxhighlight lang=apl inline>X←C1; Y←C1</source>
<syntaxhighlight lang=apl inline>⌊/X⍳Y</source>
191. Index of (first) minimum element of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X⍳⌊/X</source>
192. Test if each element of X occurs only once <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>∧/(X⍳X)=⍳⍴X</source>
193. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>∧/⎕IO=X⍳X</source>
194. Interpretation of roman numbers <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>+/Aׯ1*A<1⌽A←0,(1000 500 100 50 10 5 1)['MDCLXVI'⍳X]</source>
195. Removing elements Y from end of vector X <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(⎕IO-(~⌽X∊Y)⍳1)↓X</source>
196. Removing trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(1-(⌽' '≠X)⍳1)↓X</source>
198. Index of last occurrence of Y in X (<syntaxhighlight lang=apl inline>⎕IO-1</source> if not found) <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>((¯1 1)[2×⎕IO]+⍴X)-(⌽X)⍳Y</source>
199. Index of last occurrence of Y in X (0 if not found) <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(1+⍴X)-(⌽X)⍳Y</source>
200. Index of last occurrence of Y in X, counted from the rear <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(⌽X)⍳Y</source>
201. Index of first occurrence of G in X (circularly) after Y <syntaxhighlight lang=apl inline>X←A1; Y←I0; G←A</source>
<syntaxhighlight lang=apl inline>⎕IO+(⍴X)|Y+(Y⌽X)⍳G</source>
202. Alphabetizing X; equal alphabets in same column of Y <syntaxhighlight lang=apl inline>Y←C2; X←C</source>
<syntaxhighlight lang=apl inline>(¯1↑⍴Y)|(,Y)⍳X</source>
203. Changing index of an unfound element to zero <syntaxhighlight lang=apl inline>Y←A1; X←A</source>
<syntaxhighlight lang=apl inline>(1+⍴Y)|Y⍳X</source>
204. Replacing elements of G in set X with corresponding Y <syntaxhighlight lang=apl inline>X←A1, Y←A1, G←A</source>
<syntaxhighlight lang=apl inline>A[B/⍳⍴B]←Y[(B←B≤⍴Y)/B←X⍳A←,G] ⋄ (⍴G)⍴A</source>
205. Removing duplicate elements (nub) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>((X⍳X)=⍳⍴X)/X</source>
206. First word in X <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(¯1+X⍳' ')↑X</source>
207. Removing elements Y from beginning of vector X <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(((~X∊Y)⍳1)-⎕IO)↓X</source>
208. Removing leading zeroes <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(¯1+(X='0')⍳0)↓X</source>
209. Index of first one after index Y in X <syntaxhighlight lang=apl inline>G←I0; X←B1</source>
<syntaxhighlight lang=apl inline>Y+(Y↓X)⍳1</source>
210. Changing index of an unfound element to zero (not effective) <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>(X∊Y)×Y⍳X</source>
211. Indicator of first occurrence of each unique element of X <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(X⍳X)=⍳⍴X</source>
212. Inverting a permutation <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X⍳⍳⍴X</source>
213. Index of first differing element in vectors X and Y <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>(Y≠X)⍳1</source>
214. Which elements of X are not in set Y (difference of sets) <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>(⎕IO+⍴Y)=Y⍳X</source>
215. Changing numeric code X into corresponding name in Y <syntaxhighlight lang=apl inline>X←D; Y←D1; G←C2</source>
<syntaxhighlight lang=apl inline>G[Y⍳X;]</source>
216. Index of key Y in key vector X <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>X⍳Y</source>
217. Conversion from characters to numeric codes <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⎕AV⍳X</source>
218. Index of first satisfied condition in X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>X⍳1</source>

Outer Product <syntaxhighlight lang=apl inline>∘.!</source> <syntaxhighlight lang=apl inline>∘.⌈</source> <syntaxhighlight lang=apl inline>∘.|</source>

219. Pascal's triangle of order X (binomial coefficients) <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>⍉A∘.!A←0,⍳X</source>
220. Maximum table <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(⍳X)∘.⌈⍳X</source>
221. Number of decimals (up to Y) of elements of X <syntaxhighlight lang=apl inline>X←D; Y←I0</source>
<syntaxhighlight lang=apl inline>0+.≠(⌈(10*Y)×10*⎕IO-⍳Y+1)∘.|⌈X×10*Y</source>
222. Greatest common divisor of elements of X <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>⌈/(∧/0=A∘.|X)/A←⍳⌊/X</source>
223. Divisibility table <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>0=(⍳⌈/X)∘.|X</source>
224. All primes up to X <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(2=+⌿0=(⍳X)∘.|⍳X)/⍳X</source>

Outer Product <syntaxhighlight lang=apl inline>∘.*</source> <syntaxhighlight lang=apl inline>∘.×</source> <syntaxhighlight lang=apl inline>∘.-</source> <syntaxhighlight lang=apl inline>∘.+</source>

225. Compound interest for principals Y at rates G % in times X <syntaxhighlight lang=apl inline>X←D; Y←D; G←D</source>
<syntaxhighlight lang=apl inline>Y∘.×(1+G÷100)∘.*X</source>
226. Product of two polynomials with coefficients X and Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>+⌿(⎕IO-⍳⍴X)⌽X∘.×Y,0×1↓X</source>
228. Shur product <syntaxhighlight lang=apl inline>X←D2; Y←D2</source>
<syntaxhighlight lang=apl inline>1 2 1 2⍉X∘.×Y</source>
229. Direct matrix product <syntaxhighlight lang=apl inline>X←D2; Y←D2</source>
<syntaxhighlight lang=apl inline>1 3 2 4⍉X∘.×Y</source>
230. Multiplication table <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(⍳X)∘.×⍳X</source>
231. Replicating a dimension of rank three array X Y-fold <syntaxhighlight lang=apl inline>Y←I0; X←A3</source>
<syntaxhighlight lang=apl inline>X[;,(Y⍴1)∘.×⍳(⍴X)[2];]</source>
232. Array and its negative ('plus minus') <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X∘.×1 ¯1</source>
233. Move set of points X into first quadrant <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>1 2 1⍉X∘.-⌊/X</source>
234. Test relations of elements of X to range Y; result in ¯2..2 <syntaxhighlight lang=apl inline>X←D; Y←D; 2=¯1↑⍴Y</source>
<syntaxhighlight lang=apl inline>+/×X∘.-Y</source>
235. Occurrences of string X in string Y <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>(Y[A∘.+¯1+⍳⍴X]∧.=X)/A←(A=1↑X)/⍳⍴A←(1-⍴X)↓Y</source>
236. Sum of common parts of matrices (matrix sum) <syntaxhighlight lang=apl inline>X←D2; Y←D2</source>
<syntaxhighlight lang=apl inline>1 2 1 2⍉X∘.+Y</source>
237. Adding X to each row of Y <syntaxhighlight lang=apl inline>X←D1; Y←D2</source>
<syntaxhighlight lang=apl inline>1 1 2⍉X∘.+Y</source>
238. Adding X to each row of Y <syntaxhighlight lang=apl inline>X←D1; Y←D2</source>
<syntaxhighlight lang=apl inline>1 2 1⍉Y∘.+X</source>
240. Adding X to each column of Y <syntaxhighlight lang=apl inline>X←D1; Y←D2</source>
<syntaxhighlight lang=apl inline>2 1 2⍉X∘.+Y</source>
241. Adding X to each column of Y <syntaxhighlight lang=apl inline>X←D1; Y←D2</source>
<syntaxhighlight lang=apl inline>1 2 2⍉Y∘.+X</source>
242. Hilbert matrix of order X <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>÷¯1+(⍳X)∘.+⍳X</source>
243. Moving index of width Y for vector X <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(0,⍳(⍴X)-Y)∘.+Y</source>
244. Indices of subvectors of length Y starting at X+1 <syntaxhighlight lang=apl inline>X←I1; Y←I0</source>
<syntaxhighlight lang=apl inline>X∘.+⍳Y</source>
245. Reshaping numeric vector X into a one-column matrix <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X∘.+,0</source>
246. Annuity coefficient: X periods at interest rate Y % <syntaxhighlight lang=apl inline>X←I; Y←D</source>
<syntaxhighlight lang=apl inline>((⍴A)⍴Y÷100)÷A←⍉1-(1+Y÷100)∘.*-X</source>

Outer Product <syntaxhighlight lang=apl inline>∘.<</source> <syntaxhighlight lang=apl inline>∘.≤</source> <syntaxhighlight lang=apl inline>∘.≥</source> <syntaxhighlight lang=apl inline>∘.></source>

247. Matrix with X[i] trailing zeroes on row i <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X∘.<⌽⍳⌈/X</source>
248. Matrix with X[i] leading zeroes on row i <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X∘.<⍳⌈/X</source>
249. Distribution of X into intervals between Y <syntaxhighlight lang=apl inline>X←D; Y←D1</source>
<syntaxhighlight lang=apl inline>+/((¯1↓Y)∘.≤X)∧(1↓Y)∘.>X</source>
250. Histogram (distribution barchart; down the page) <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>' ⎕'[⎕IO+(⌽⍳⌈/A)∘.≤A←+/(⍳1+(⌈/X)-⌊/X)∘.=X]</source>
251. Barchart of integer values (down the page) <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>' ⎕'[⎕IO+(⌽⍳⌈/X)∘.≤X]</source>
252. Test if X is an upper triangular matrix <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>∧/,(0≠X)≤A∘.≤A←⍳1↑⍴X</source>
253. Number of ?s intersecting ?s (X=starts, Y=stops) <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>+/A∧⍉A←X∘.≤Y</source>
254. Contour levels Y at points with altitudes X <syntaxhighlight lang=apl inline>X←D0; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[+⌿Y∘.≤X]</source>
255. X×X upper triangular matrix <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(⍳X)∘.≤⍳X</source>
256. Classification of elements Y into X classes of equal size <syntaxhighlight lang=apl inline>X←I0; Y←D1</source>
<syntaxhighlight lang=apl inline>+/(A×X÷⌈/A←Y-⌊/Y)∘.≥¯1+⍳X</source>
257. Matrix with X[i] trailing ones on row i <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X∘.≥⌽⍳⌈/X</source>
258. Comparison table <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X∘.≥⍳⌈/X,0</source>
259. Barchart of X with height Y (across the page) <syntaxhighlight lang=apl inline>X←D1; Y←D0</source>
<syntaxhighlight lang=apl inline>' ⎕'[⎕IO+X∘.≥(⌈/X)×(⍳Y)÷Y]</source>
260. Barchart of integer values (across the page) <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>' ⎕'[⎕IO+X∘.≥⍳⌈/X]</source>
261. Matrix with X[i] leading ones on row i <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>X∘.≥⍳⌈/X</source>
263. Test if X is a lower triangular matrix <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>∧/,(0≠X)≤A∘.≥A←⍳1↑⍴X</source>
264. Test if X is within range [ Y[1],Y[2] ) <syntaxhighlight lang=apl inline>X←D; Y←D1</source>
<syntaxhighlight lang=apl inline>≠/X∘.≥Y</source>
265. Ordinal numbers of words in X that indices Y point to <syntaxhighlight lang=apl inline>X←C1; Y←I</source>
<syntaxhighlight lang=apl inline>⎕IO++/Y∘.≥(' '=X)/⍳⍴X</source>
266. Which class do elements of X belong to <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>+/X∘.≥0 50 100 1000</source>
267. X×X lower triangular matrix <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(⍳X)∘.≥⍳X</source>
268. Moving all blanks to end of each row <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(⍴X)⍴(,(+/A)∘.>-⎕IO-⍳¯1↑⍴X)\(,A←X≠' ')/,X</source>
269. Justifying right fields of X (lengths Y) to length G <syntaxhighlight lang=apl inline>X←A1; Y←I1; G←I0</source>
<syntaxhighlight lang=apl inline>(,Y∘.>⌽(⍳G)-⎕IO)\X</source>
270. Justifying left fields of X (lengths Y) to length G <syntaxhighlight lang=apl inline>X←A1; Y←I1; G←I0</source>
<syntaxhighlight lang=apl inline>(,Y∘.>(⍳G)-⎕IO)\X</source>

Outer Product <syntaxhighlight lang=apl inline>∘.≠</source> <syntaxhighlight lang=apl inline>∘.=</source>

271. Indices of elements of Y in corr. rows of X (<syntaxhighlight lang=apl inline>X[i;]⍳Y[i;]</source>) <syntaxhighlight lang=apl inline>X←A2; Y←A2</source>
<syntaxhighlight lang=apl inline>1++/∧\1 2 1 3⍉Y∘.≠X</source>
273. Indicating equal elements of X as a logical matrix <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>⍉X∘.=(1 1⍉<\X∘.=X)/X</source>
275. Changing connection matrix X (<syntaxhighlight lang=apl inline>¯1 → 1</source>) to a node matrix <syntaxhighlight lang=apl inline>X←I2</source>
<syntaxhighlight lang=apl inline>(1 ¯1∘.=⍉X)+.×⍳1↑⍴⎕←X</source>
276. Sums according to codes G <syntaxhighlight lang=apl inline>X←A; Y←D; G←A</source>
<syntaxhighlight lang=apl inline>(G∘.=X)+.×Y</source>
277. Removing duplicate elements (nub) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(1 1⍉<\X∘.=X)/X</source>
278. Changing node matrix X (starts,ends) to a connection matrix <syntaxhighlight lang=apl inline>X←I2</source>
<syntaxhighlight lang=apl inline>-/(⍳⌈/,X)∘.=⍉X</source>
279. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>∨/∧/0 1∘.=X</source>
280. Test if elements of X belong to corr. row of Y (<syntaxhighlight lang=apl inline>X[i;]∊Y[i;]</source>) <syntaxhighlight lang=apl inline>X←A2; Y←A2; 1↑⍴X←→1↑⍴Y</source>
<syntaxhighlight lang=apl inline>∨/1 2 1 3⍉X∘.=Y</source>
281. Test if X is a permutation vector <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>∧/1=+⌿X∘.=⍳⍴X</source>
282. Occurrences of string X in string Y <syntaxhighlight lang=apl inline>X←C1; Y←C1</source>
<syntaxhighlight lang=apl inline>(∧⌿(¯1+⍳⍴X)⌽(X∘.=Y),0)/⍳1+⍴Y</source>
283. Division to Y classes with width H, minimum G <syntaxhighlight lang=apl inline>X←D; Y←I0; G←D0; H←D0</source>
<syntaxhighlight lang=apl inline>+/(⍳Y)∘.=⌈(X-G)÷H</source>
285. Repeat matrix <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>(((¯1⌽~A)∧A←(¯1↓X=1⌽X),0)/Y)∘.=Y</source>
286. X×X identity matrix <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(⍳X)∘.=⍳X</source>

Inner Product <syntaxhighlight lang=apl inline>⌈.×</source> <syntaxhighlight lang=apl inline>⌊.×</source> <syntaxhighlight lang=apl inline>⌊.+</source> <syntaxhighlight lang=apl inline>×.○</source> <syntaxhighlight lang=apl inline>×.*</source> <syntaxhighlight lang=apl inline>+.*</source>

287. Maxima of elements of subsets of X specified by Y <syntaxhighlight lang=apl inline>X←A1; Y←B</source>
<syntaxhighlight lang=apl inline>A+(X-A←⌊/X)⌈.×Y</source>
288. Indices of last non-blanks in rows <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(' '≠X)⌈.×⍳¯1↑⍴X</source>
289. Maximum of X with weights Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y⌈.×X</source>
290. Minimum of X with weights Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y⌊.×X</source>
292. Extending a distance table to next leg <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>X←X⌊.+X</source>
293. A way to combine trigonometric functions (sin X cos Y) <syntaxhighlight lang=apl inline>X←D0; Y←D0</source>
<syntaxhighlight lang=apl inline>1 2×.○X,Y</source>
294. Sine of a complex number <syntaxhighlight lang=apl inline>X←D; 2=1↑⍴X</source>
<syntaxhighlight lang=apl inline>(2 2⍴1 6 2 5)×.○X</source>
295. Products over subsets of X specified by Y <syntaxhighlight lang=apl inline>X←A1; Y←B</source>
<syntaxhighlight lang=apl inline>X×.*Y</source>
296. Sum of squares of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X+.*2</source>
297. Randomizing random numbers (in <syntaxhighlight lang=apl inline>⎕LX</source> in a workspace) <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⎕RL←⎕TS+.*2</source>

Inner Product <syntaxhighlight lang=apl inline>∨.∧</source> <syntaxhighlight lang=apl inline><.<</source> <syntaxhighlight lang=apl inline><.≤</source> <syntaxhighlight lang=apl inline><.≥</source> <syntaxhighlight lang=apl inline>≤.≥</source> <syntaxhighlight lang=apl inline>>.></source>

298. Extending a transitive binary relation <syntaxhighlight lang=apl inline>X←B2</source>
<syntaxhighlight lang=apl inline>X←X∨.∧X</source>
299. Test if X is within range [ Y[1;],Y[2;] ) <syntaxhighlight lang=apl inline>X←D0; Y←D2; 1↑⍴Y ←→ 2</source>
<syntaxhighlight lang=apl inline>X<.<Y</source>
300. Test if X is within range ( Y[1;],Y[2;] ] <syntaxhighlight lang=apl inline>X←D0; Y←D2; 1↑⍴Y ←→ 2</source>
<syntaxhighlight lang=apl inline>X<.≤Y</source>
301. Test if X is within range ( Y[1;],Y[2;] ] <syntaxhighlight lang=apl inline>X←D; Y←D2; 1↑⍴Y ←→ 2</source>
<syntaxhighlight lang=apl inline>X<.≤Y</source>
302. Test if the elements of X are ascending <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X<.≥1⌽X</source>
303. Test if X is an integer within range [ G,H ) <syntaxhighlight lang=apl inline>X←I0; G←I0; H←I0</source>
<syntaxhighlight lang=apl inline>~X≤.≥(⌈X),G,H</source>
304. Test if X is within range ( Y[1;],Y[2;] ] <syntaxhighlight lang=apl inline>X←D; Y←D2; 1↑⍴Y ←→ 2</source>
<syntaxhighlight lang=apl inline>(X,[.1+⍴⍴X]X)>.>Y</source>

Inner Product <syntaxhighlight lang=apl inline>∨.≠</source> <syntaxhighlight lang=apl inline>∧.=</source> <syntaxhighlight lang=apl inline>+.≠</source> <syntaxhighlight lang=apl inline>+.=</source>

306. Removing trailing blank columns <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(⌽∨\⌽' '∨.≠X)/X</source>
307. Removing leading blank rows <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(∨\X∨.≠' ')⌿X</source>
308. Removing leading blank columns <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(∨\' '∨.≠X)/X</source>
309. Index of first occurrences of rows of X as rows of Y <syntaxhighlight lang=apl inline>X←A, Y←A2</source>
<syntaxhighlight lang=apl inline>⎕IO++⌿∧⍀Y∨.≠⍉X</source>
310. <syntaxhighlight lang=apl inline>X⍳Y</source> for rows of matrices <syntaxhighlight lang=apl inline>X←A2; Y←A2</source>
<syntaxhighlight lang=apl inline>⎕IO++⌿∧⍀X∨.≠⍉Y</source>
311. Removing duplicate blank rows <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(A∨1↓1⌽1,A←X∨.≠' ')⌿X</source>
312. Removing duplicate blank columns <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(A∨1,¯1↓A←' '∨.≠X)/X</source>
313. Removing blank columns <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(' '∨.≠X)/X</source>
314. Removing blank rows <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(X∨.≠' ')⌿X</source>
315. Test if rows of X contain elements differing from Y <syntaxhighlight lang=apl inline>X←A; Y←A0</source>
<syntaxhighlight lang=apl inline>X∨.≠Y</source>
316. Removing trailing blank rows <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(-2↑+/∧\⌽X∧.=' ')↓X</source>
317. Removing duplicate rows <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(∨⌿<\X∧.=⍉X)⌿X</source>
318. Removing duplicate rows <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(1 1⍉<\X∧.=⍉X)⌿X</source>
319. Test if circular lists are equal (excluding phase) <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>∨/Y∧.=⍉(⍳⍴X)⌽(2⍴⍴X)⍴X</source>
320. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>X∧.=∨/X</source>
321. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>X∧.=∧/X</source>
322. Rows of matrix X starting with string Y <syntaxhighlight lang=apl inline>X←A2; Y←A1</source>
<syntaxhighlight lang=apl inline>((((1↑⍴X),⍴Y)↑X)∧.=Y)⌿X</source>
323. Occurrences of string X in string Y <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>((-A)↓X∧.=(A,1+⍴Y)⍴Y)/⍳(⍴Y)+1-A←⍴X</source>
324. Test if vector Y is a row of array X <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>1∊X∧.=Y</source>
325. Comparing vector Y with rows of array X <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>X∧.=Y</source>
326. Word lengths of words in list X <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>X+.≠' '</source>
327. Number of occurrences of scalar X in array Y <syntaxhighlight lang=apl inline>X←A0; Y←A</source>
<syntaxhighlight lang=apl inline>X+.=,Y</source>
328. Counting pairwise matches (equal elements) in two vectors <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>X+.=Y</source>

Inner Product <syntaxhighlight lang=apl inline>-.÷</source> <syntaxhighlight lang=apl inline>+.÷</source> <syntaxhighlight lang=apl inline>+.×</source>

329. Sum of alternating reciprocal series Y÷X <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y-.÷X</source>
330. Limits X to fit in <syntaxhighlight lang=apl inline>⍕</source> field Y[1 2] <syntaxhighlight lang=apl inline>X←D; Y←I1</source>
<syntaxhighlight lang=apl inline>(X⌈1↓A)⌊1↑A←(2 2⍴¯1 1 1 ¯.1)+.×10*(-1↓Y),-/Y+Y>99 0</source>
331. Value of polynomial with coefficients Y at point X <syntaxhighlight lang=apl inline>X←D0; Y←D</source>
<syntaxhighlight lang=apl inline>(X*¯1+⍳⍴Y)+.×⌽Y</source>
332. Arithmetic average (mean value) of X weighted by Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>(Y+.×X)÷⍴X</source>
333. Scalar (dot) product of vectors <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y+.×X</source>
334. Sum of squares of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X+.×X</source>
335. Summation over subsets of X specified by Y <syntaxhighlight lang=apl inline>X←A1; Y←B</source>
<syntaxhighlight lang=apl inline>X+.×Y</source>
336. Matrix product <syntaxhighlight lang=apl inline>X←D; Y←D; ¯1↑⍴X ←→ 1↑⍴Y</source>
<syntaxhighlight lang=apl inline>X+.×Y</source>
337. Sum of reciprocal series Y÷X <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>Y+.÷X</source>

Scan <syntaxhighlight lang=apl inline>⌈\</source> <syntaxhighlight lang=apl inline>⌊\</source> <syntaxhighlight lang=apl inline>×\</source> <syntaxhighlight lang=apl inline>-\</source>

338. Groups of ones in Y pointed to by X (or trailing parts) <syntaxhighlight lang=apl inline>X←B; Y←B</source>
<syntaxhighlight lang=apl inline>Y∧A=⌈\X×A←+\Y>¯1↓0,Y</source>
339. Test if X is in ascending order along direction Y <syntaxhighlight lang=apl inline>X←D; Y←I0</source>
<syntaxhighlight lang=apl inline>∧/[Y]X=⌈\[Y]X</source>
340. Duplicating element of X belonging to <syntaxhighlight lang=apl inline>Y,1↑X</source> until next found <syntaxhighlight lang=apl inline>X←A1; Y←B1</source>
<syntaxhighlight lang=apl inline>X[1⌈⌈\Y×⍳⍴Y]</source>
341. Test if X is in descending order along direction Y <syntaxhighlight lang=apl inline>X←D; Y←I0</source>
<syntaxhighlight lang=apl inline>∧/[Y]X=⌊\[Y]X</source>
342. Value of Taylor series with coefficients Y at point X <syntaxhighlight lang=apl inline>X←D0; Y←D1</source>
<syntaxhighlight lang=apl inline>+/Y××\1,X÷⍳¯1+⍴Y</source>
343. Alternating series (1 ¯1 2 ¯2 3 ¯3 ...) <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>-\⍳X</source>

Scan <syntaxhighlight lang=apl inline>⍲\</source> <syntaxhighlight lang=apl inline><\</source> <syntaxhighlight lang=apl inline>≤\</source> <syntaxhighlight lang=apl inline>≠\</source>

346. Value of saddle point <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>(<\,(X=(⍴X)⍴⌈⌿X)∧X=⍉(⌽⍴X)⍴⌊/X)/,X</source>
348. First one (turn off all ones after first one) <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline><\X</source>
350. Not first zero (turn on all zeroes after first zero) <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>≤\X</source>
351. Running parity (≠\) over subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>≠\Y≠X\A≠¯1↓0,A←X/≠\¯1↓0,Y</source>
352. Vector <syntaxhighlight lang=apl inline>(X[1]⍴1),(X[2]⍴0),(X[3]⍴1),...</source> <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>≠\(⍳+/X)∊+\⎕IO,X</source>
353. Not leading zeroes(<syntaxhighlight lang=apl inline>∨\</source>) in each subvector of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>≠\(Y∨X)\A≠¯1↓0,A←(Y∨X)/Y</source>
354. Leading ones (<syntaxhighlight lang=apl inline>∧\</source>) in each subvector of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>~≠\(Y≤X)\A≠¯1↓0,A←~(Y≤X)/Y</source>
355. Locations of texts between and including quotes <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>A∨¯1↓0,A←≠\X='</source>
356. Locations of texts between quotes <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>A∧¯1↓0,A←≠\X='</source>
357. Joining pairs of ones <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>X∨≠\X</source>
358. Places between pairs of ones <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>(~X)∧≠\X</source>
359. Running parity <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>≠\X</source>

Scan <syntaxhighlight lang=apl inline>∨\</source> <syntaxhighlight lang=apl inline>∧\</source>

360. Removing leading and trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>((⌽∨\⌽A)∧∨\A←' '≠X)/X</source>
361. First group of ones <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>X∧∧\X=∨\X</source>
362. Removing trailing blank columns <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(⌽∨\⌽∨⌿' '≠X)/X</source>
363. Removing trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(⌽∨\⌽' '≠X)/X</source>
364. Removing leading blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(∨\' '≠X)/X</source>
365. Not leading zeroes (turn on all zeroes after first one) <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>∨\X</source>
366. Centering character array X with ragged edges <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(A-⌊0.5×(A←+/∧\⌽A)++/∧\A←' '=⌽X)⌽X</source>
367. Decommenting a matrix representation of a function (<syntaxhighlight lang=apl inline>⎕CR</source>) <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>(∨/A)⌿(⍴X)⍴(,A)\(,A←∧\('⍝'≠X)∨≠\X=')/,X</source>
369. Centering character array X with only right edge ragged <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(-⌊0.5×+/∧\' '=⌽X)⌽X</source>
370. Justifying right <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(-+/∧\⌽' '=X)⌽X</source>
371. Removing trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(-+/∧\⌽' '=X)↓X</source>
372. Justifying left <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>(+/∧\' '=X)⌽X</source>
373. Editing X with Y '-wise <syntaxhighlight lang=apl inline>X←C1; Y←C1</source>
<syntaxhighlight lang=apl inline>((~(⍴A↑X)↑'/'=Y)/A↑X),(1↓A↓Y),(A←+/∧\Y≠',')↓X</source>
374. Removing leading blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(+/∧\' '=X)↓X</source>
375. Indices of first blanks in rows of array X <syntaxhighlight lang=apl inline>X←C</source>
<syntaxhighlight lang=apl inline>⎕IO++/∧\' '≠X</source>
377. Leading ones (turn off all ones after first zero) <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>∧\X</source>

Scan <syntaxhighlight lang=apl inline>+\</source>

378. Vector (<syntaxhighlight lang=apl inline>X[1]⍴1),(Y[1]⍴0),(X[2]⍴1),...</source> <syntaxhighlight lang=apl inline>X←I1; Y←I1</source>
<syntaxhighlight lang=apl inline>(⍳+/X,Y)∊+\1+¯1↓0,((⍳+/X)∊+\X)\Y</source>
379. Replicate Y[i] X[i] times (for all i) <syntaxhighlight lang=apl inline>X←I1; Y←A1</source>
<syntaxhighlight lang=apl inline>((X≠0)/Y)[+\¯1⌽(⍳+/X)∊+\X]</source>
380. Vector (<syntaxhighlight lang=apl inline>Y[1]+⍳X[1]),(Y[2]+⍳X[2]),(Y[3]+⍳X[3]),...</source> <syntaxhighlight lang=apl inline>X←I1; Y←I1; ⍴X←→⍴Y</source>
<syntaxhighlight lang=apl inline>⎕IO++\1+((⍳+/X)∊+\⎕IO,X)\Y-¯1↓1,X+Y</source>
381. Replicate Y[i] X[i] times (for all i) <syntaxhighlight lang=apl inline>X←I1; Y←A1</source>
<syntaxhighlight lang=apl inline>Y[+\(⍳+/X)∊¯1↓1++\0,X]</source>
382. Replicate Y[i] X[i] times (for all i) <syntaxhighlight lang=apl inline>X←I1; Y←A1</source>
<syntaxhighlight lang=apl inline>Y[⎕IO++\(⍳+/X)∊⎕IO++\X]</source>
383. Cumulative sums (+\) over subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>+\Y-X\A-¯1↓0,A←X/+\¯1↓0,Y</source>
384. Sums over (+/) subvectors of Y, lengths in X <syntaxhighlight lang=apl inline>X←I1; Y←D1</source>
<syntaxhighlight lang=apl inline>A-¯1↓0,A←(+\Y)[+\X]</source>
386. X first figurate numbers <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>+\+\⍳X</source>
387. Insert vector for X[i] zeroes after i:th subvector <syntaxhighlight lang=apl inline>X←I1; Y←B1</source>
<syntaxhighlight lang=apl inline>(⍳(⍴Y)++/X)∊+\1+¯1↓0,(1⌽Y)\X</source>
388. Open a gap of X[i] after Y[G[i]] (for all i) <syntaxhighlight lang=apl inline>X←I1; Y←A1; G←I1</source>
<syntaxhighlight lang=apl inline>((⍳(⍴Y)++/X)∊+\1+¯1↓0,((⍳⍴Y)∊G)\X)\Y</source>
389. Open a gap of X[i] before Y[G[i]] (for all i) <syntaxhighlight lang=apl inline>X←I1; Y←A1; G←I1</source>
<syntaxhighlight lang=apl inline>((⍳(⍴Y)++/X)∊+\1+((⍳⍴Y)∊G)\X)\Y</source>
390. Changing lengths X of subvectors to starting indicators <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>A←(+/X)⍴0 ⋄ A[+\¯1↓⎕IO,X]←1 ⋄ A</source>
391. Changing lengths X of subvectors to ending indicators <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>(⍳+/X)∊(+\X)-~⎕IO</source>
392. Changing lengths X of subvectors to starting indicators <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>(⍳+/X)∊+\⎕IO,X</source>
393. Insert vector for X[i] elements before i:th element <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>(⍳+/A)∊+\A←1+X</source>
394. Sums over (+/) subvectors of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←D1</source>
<syntaxhighlight lang=apl inline>A-¯1↓0,A←(1⌽X)/+\Y</source>
395. Fifo stock Y decremented with X units <syntaxhighlight lang=apl inline>Y←D1; X←D0</source>
<syntaxhighlight lang=apl inline>G-¯1↓0,G←0⌈(+\Y)-X</source>
396. Locations of texts between and including quotes <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>A∨¯1↓0,A←2|+\X='</source>
397. Locations of texts between quotes <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>A∧¯1↓0,A←2|+\X='</source>
398. X:th subvector of Y (subvectors separated by Y[1]) <syntaxhighlight lang=apl inline>Y←A1; X←I0</source>
<syntaxhighlight lang=apl inline>1↓(X=+\Y=1↑Y)/Y</source>
399. Locating field number Y starting with first element of X <syntaxhighlight lang=apl inline>Y←I0; X←C1</source>
<syntaxhighlight lang=apl inline>(Y=+\X=1↑X)/X</source>
400. Sum elements of X marked by succeeding identicals in Y <syntaxhighlight lang=apl inline>X←D1; Y←D1</source>
<syntaxhighlight lang=apl inline>A-¯1↓0,A←(Y≠1↓Y,0)/+\X</source>
401. Groups of ones in Y pointed to by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>Y∧A∊(X∧Y)/A←+\Y>¯1↓0,Y</source>
402. ith starting indicators X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>(+\X)∊Y/⍳⍴Y</source>
403. G:th subvector of Y (subvectors indicated by X) <syntaxhighlight lang=apl inline>X←B1; Y←A1; G←I0</source>
<syntaxhighlight lang=apl inline>(G=+\X)/Y</source>
404. Running sum of Y consecutive elements of X <syntaxhighlight lang=apl inline>X←D1; Y←I0</source>
<syntaxhighlight lang=apl inline>((Y-1)↓A)-0,(-Y)↓A←+\X</source>
405. Depth of parentheses <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>+\('('=X)-¯1↓0,')'=X</source>
406. Starting positions of subvectors having lengths X <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>+\¯1↓⎕IO,X</source>
407. Changing lengths X of subvectors of Y to ending indicators <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>(⍳⍴Y)∊(+\X)-~⎕IO</source>
408. Changing lengths X of subvectors of Y to starting indicators <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>(⍳⍴Y)∊+\⎕IO,X</source>
409. X first triangular numbers <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>+\⍳X</source>
410. Cumulative sum <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>+\X</source>

Reduction <syntaxhighlight lang=apl inline>○/</source> <syntaxhighlight lang=apl inline>÷/</source> <syntaxhighlight lang=apl inline>-/</source> <syntaxhighlight lang=apl inline>×/</source>

411. Complementary angle (arccos sin X) <syntaxhighlight lang=apl inline>X←D0</source>
<syntaxhighlight lang=apl inline>○/¯2 1,X</source>
412. Evaluating a two-row determinant <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>-/×/0 1⊖X</source>
413. Evaluating a two-row determinant <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>-/×⌿0 1⌽X</source>
414. Area of triangle with side lengths in X (Heron's formula) <syntaxhighlight lang=apl inline>X←D1; 3 ←→ ⍴X</source>
<syntaxhighlight lang=apl inline>(×/(+/X÷2)-0,X)*.5</source>
415. Juxtapositioning planes of rank 3 array X <syntaxhighlight lang=apl inline>X←A3</source>
<syntaxhighlight lang=apl inline>(×⌿2 2⍴1,⍴X)⍴2 1 3⍉X</source>
416. Number of rows in array X (also of a vector) <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>×/¯1↓⍴X</source>
417. (Real) solution of quadratic equation with coefficients X <syntaxhighlight lang=apl inline>X←D1; 3 ←→ ⍴X</source>
<syntaxhighlight lang=apl inline>(-X[2]-¯1 1×((X[2]*2)-×/4,X[1 3])*.5)÷2×X[1]</source>
418. Reshaping planes of rank 3 array to rows of a matrix <syntaxhighlight lang=apl inline>X←A3</source>
<syntaxhighlight lang=apl inline>(×/2 2⍴1,⍴X)⍴X</source>
419. Reshaping planes of rank 3 array to a matrix <syntaxhighlight lang=apl inline>X←A3</source>
<syntaxhighlight lang=apl inline>(×/2 2⍴(⍴X),1)⍴X</source>
420. Number of elements (also of a scalar) <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>×/⍴X</source>
421. Product of elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>×/X</source>
422. Alternating product <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>÷/X</source>
423. Centering text line X into a field of width Y <syntaxhighlight lang=apl inline>X←C1; Y←I0</source>
<syntaxhighlight lang=apl inline>Y↑((⌊-/.5×Y,⍴X)⍴' '),X</source>
424. Alternating sum <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>-/X</source>

Reduction <syntaxhighlight lang=apl inline>⌈/</source> <syntaxhighlight lang=apl inline>⌊/</source>

425. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(⌈/X)=⌊/X</source>
426. Size of range of elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(⌈/X)-⌊/X</source>
427. Conversion of set of positive integers X to a mask <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>(⍳⌈/X)∊X</source>
428. Negative infinity; the smallest representable value <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⌈/⍳0</source>
429. Vectors as column matrices in catenation beneath each other <syntaxhighlight lang=apl inline>X←A1/2; Y←A1/2</source>
<syntaxhighlight lang=apl inline>X,[1+.5×⌈/(⍴⍴X),⍴⍴Y]Y</source>
430. Vectors as row matrices in catenation upon each other <syntaxhighlight lang=apl inline>X←A1/2; Y←A1/2</source>
<syntaxhighlight lang=apl inline>X,[.5×⌈/(⍴⍴X),⍴⍴Y]Y</source>
431. Quick membership (<syntaxhighlight lang=apl inline>∊</source>) for positive integers <syntaxhighlight lang=apl inline>X←I1; Y←I1</source>
<syntaxhighlight lang=apl inline>A←(⌈/X,Y)⍴0 ⋄ A[Y]←1 ⋄ A[X]</source>
432. Positive maximum, at least zero (also for empty X) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⌈/X,0</source>
433. Maximum of elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⌈/X</source>
434. Positive infinity; the largest representable value <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⌊/⍳0</source>
435. Minimum of elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>⌊/X</source>

Reduction <syntaxhighlight lang=apl inline>∨/</source> <syntaxhighlight lang=apl inline>⍲/</source> <syntaxhighlight lang=apl inline>≠/</source>

436. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>⍲/0 1∊X</source>
437. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>(∧/X)∨~∨/X</source>
438. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>(∧/X)=∨/X</source>
439. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>∧/X÷∨/X</source>
440. Removing duplicate rows from ordered matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(¯1⌽1↓(∨/X≠¯1⊖X),1)⌿X</source>
441. Vector having as many ones as X has rows <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>∨/0/X</source>
442. Test if X and Y have elements in common <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>∨/Y∊X</source>
443. None, neither <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>~∨/X</source>
444. Any, anyone <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>∨/X</source>
445. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>≠/0 1∊X</source>
446. Parity <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>≠/X</source>

Reduction <syntaxhighlight lang=apl inline>∧/</source>

447. Number of areas intersecting areas in X <syntaxhighlight lang=apl inline>X←D3 (n × 2 × dim)</source>
<syntaxhighlight lang=apl inline>+/A∧⍉A←∧/X[;A⍴1;]≤2 1 3⍉X[;(A←1↑⍴X)⍴2;]</source>
448. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>∧/X/1⌽X</source>
449. Comparison of successive rows <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>∧/X=1⊖X</source>
450. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>∧/X=1⌽X</source>
451. Test if X is a valid APL name <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>∧/((1↑X)∊10↓A),X∊A←'0..9A..Za..z'</source>
452. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>∧/X=1↑X</source>
453. Identity of two sets <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>∧/(X∊Y),Y∊X</source>
454. Test if X is a permutation vector <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>∧/(⍳⍴X)∊X</source>
455. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>~∧/X∊~X</source>
456. Test if X is boolean <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>∧/,X∊0 1</source>
457. Test if Y is a subset of X (<syntaxhighlight lang=apl inline>Y ⊂ X</source>) <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>∧/Y∊X</source>
458. Test if arrays of equal shape are identical <syntaxhighlight lang=apl inline>X←A; Y←A; ⍴X ←→ ⍴Y</source>
<syntaxhighlight lang=apl inline>∧/,X=Y</source>
459. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>∧/X=X[1]</source>
460. Blank rows <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>∧/' '=X</source>
461. All, both <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>∧/X</source>

Reduction <syntaxhighlight lang=apl inline>+/</source>

462. Standard deviation of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>((+/(X-(+/X)÷⍴X)*2)÷⍴X)*.5</source>
463. Y:th moment of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(+/(X-(+/X)÷⍴X)*Y)÷⍴X</source>
464. Variance (dispersion) of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(+/(X-(+/X)÷⍴X)*2)÷⍴X</source>
465. Arithmetic average (mean value), also for an empty array <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>(+/,X)÷1⌈⍴,X</source>
466. Test if all elements of vector X are equal <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>0=(⍴X)|+/X</source>
467. Average (mean value) of columns of matrix X <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>(+⌿X)÷1↑(⍴X),1</source>
468. Average (mean value) of rows of matrix X <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>(+/X)÷¯1↑1,⍴X</source>
469. Number of occurrences of scalar X in array Y <syntaxhighlight lang=apl inline>X←A0; Y←A</source>
<syntaxhighlight lang=apl inline>+/X=,Y</source>
470. Average (mean value) of elements of X along direction Y <syntaxhighlight lang=apl inline>X←D; Y←I0</source>
<syntaxhighlight lang=apl inline>(+/[Y]X)÷(⍴X)[Y]</source>
471. Arithmetic average (mean value) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(+/X)÷⍴X</source>
472. Resistance of parallel resistors <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>÷+/÷X</source>
473. Sum of elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>+/X</source>
474. Row sum of a matrix <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>+/X</source>
475. Column sum of a matrix <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>+⌿X</source>
476. Reshaping one-element vector X into a scalar <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>+/X</source>
477. Number of elements satisfying condition X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>+/X</source>

Reverse <syntaxhighlight lang=apl inline>⌽</source> <syntaxhighlight lang=apl inline>⊖</source>

478. Scan from end with function <syntaxhighlight lang=apl inline>⍺</source> <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⌽⍺\⌽X</source>
479. The index of positive integers in Y <syntaxhighlight lang=apl inline>X←I; Y←I1</source>
<syntaxhighlight lang=apl inline>A←9999⍴⎕IO+⍴Y ⋄ A[⌽Y]←⌽⍳⍴Y ⋄ A[X]</source>
480. 'Transpose' of matrix X with column fields of width Y <syntaxhighlight lang=apl inline>X←A2; G←I0</source>
<syntaxhighlight lang=apl inline>((⌽A)×1,Y)⍴2 1 3⍉(1⌽Y,A←(⍴X)÷1,Y)⍴X</source>
482. Adding X to each column of Y <syntaxhighlight lang=apl inline>X←D1; Y←D; (⍴X)=1↑⍴Y</source>
<syntaxhighlight lang=apl inline>Y+⍉(⌽⍴Y)⍴X</source>
483. Matrix with shape of Y and X as its columns <syntaxhighlight lang=apl inline>X←A1; Y←A2</source>
<syntaxhighlight lang=apl inline>⍉(⌽⍴Y)⍴X</source>
484. Derivate of polynomial X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>¯1↓X×⌽¯1+⍳⍴X</source>
485. Reverse vector X on condition Y <syntaxhighlight lang=apl inline>X←A1; Y←B0</source>
<syntaxhighlight lang=apl inline>,⌽[⎕IO+Y](1,⍴X)⍴X</source>
486. Reshaping vector X into a one-column matrix <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(⌽1,⍴X)⍴X</source>
487. Avoiding parentheses with help of reversal <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>(⌽1, ...)</source>

Rotate <syntaxhighlight lang=apl inline>⌽</source> <syntaxhighlight lang=apl inline>⊖</source>

488. Vector (cross) product of vectors <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>((1⌽X)ׯ1⌽Y)-(¯1⌽X)×1⌽Y</source>
489. A magic square, side X <syntaxhighlight lang=apl inline>X←I0; 1=2|X</source>
<syntaxhighlight lang=apl inline>A⊖(A←(⍳X)-⌈X÷2)⌽(X,X)⍴⍳X×X</source>
490. Removing duplicates from an ordered vector <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(¯1⌽1↓(X≠¯1⌽X),1)/X</source>
491. An expression giving itself <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>1⌽22⍴11⍴1⌽22⍴11⍴</source>
492. Transpose matrix X on condition Y <syntaxhighlight lang=apl inline>X←A2; Y←B0</source>
<syntaxhighlight lang=apl inline>(Y⌽1 2)⍉X</source>
493. Any element true (<syntaxhighlight lang=apl inline>∨/</source>) on each subvector of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>(X/Y)≥A/1⌽A←(Y∨X)/X</source>
494. All elements true (<syntaxhighlight lang=apl inline>∧/</source>) on each subvector of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>(X/Y)∧A/1⌽A←(Y≤X)/X</source>
495. Removing leading, multiple and trailing Y's <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>(1↑A)↓(A⍲1⌽A←Y=X)/X</source>
496. Changing starting indicators X of subvectors to lengths <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>A-¯1↓0,A←(1⌽X)/⍳⍴X</source>
498. (Cyclic) compression of successive blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(A∨1⌽A←X≠' ')/X</source>
499. Aligning columns of matrix X to diagonals <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(1-⍳¯1↑⍴X)⌽X</source>
500. Aligning diagonals of matrix X to columns <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(¯1+⍳¯1↑⍴X)⌽X</source>
501. Diagonal matrix with elements of X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>0 ¯1↓(-⍳⍴X)⌽((2⍴⍴X)⍴0),X</source>
502. Test if elements differ from previous ones (non-empty X) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>1,1↓X≠¯1⌽X</source>
503. Test if elements differ from next ones (non-empty X) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(¯1↓X≠1⌽X),1</source>
504. Replacing first element of X with Y <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>¯1⌽1↓X,Y</source>
505. Replacing last element of X with Y <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>1⌽¯1↓Y,X</source>
506. Ending points for X in indices pointed by Y <syntaxhighlight lang=apl inline>X←A1; Y←I1</source>
<syntaxhighlight lang=apl inline>1⌽(⍳⍴X)∊Y</source>
507. Leftmost neighboring elements cyclically <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>¯1⌽X</source>
508. Rightmost neighboring elements cyclically <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>1⌽X</source>

Transpose <syntaxhighlight lang=apl inline>⍉</source>

509. Applying to columns action defined on rows <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>⍉ ... ⍉X</source>
510. Retrieving scattered elements Y from matrix X <syntaxhighlight lang=apl inline>X←A2; Y←I2</source>
<syntaxhighlight lang=apl inline>1 1⍉X[Y[1;];Y[2;]]</source>
511. Successive transposes of G (X after Y: <syntaxhighlight lang=apl inline>X⍉Y⍉G</source>) <syntaxhighlight lang=apl inline>X←I1; Y←I1</source>
<syntaxhighlight lang=apl inline>X[Y]⍉G</source>
512. Major diagonal of array X <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>(1*⍴X)⍉X</source>
513. Reshaping a 400×12 character matrix to fit into one page <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>40 120⍴2 1 3⍉10 40 12⍴X</source>
514. Transpose of planes of a rank three array <syntaxhighlight lang=apl inline>X←A3</source>
<syntaxhighlight lang=apl inline>1 3 2⍉X</source>
515. Major diagonal of matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>1 1⍉X</source>
516. Selecting specific elements from a 'large' outer product <syntaxhighlight lang=apl inline>X←A; Y←A; G←I1</source>
<syntaxhighlight lang=apl inline>G⍉X∘.⍺Y</source>
517. Test for antisymmetricity of square matrix X <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>~0∊X=-⍉X</source>
518. Test for symmetricity of square matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>~0∊X=⍉X</source>
519. Matrix with X columns Y <syntaxhighlight lang=apl inline>X←I0; Y←D1</source>
<syntaxhighlight lang=apl inline>⍉(X,⍴Y)⍴Y</source>

Maximum <syntaxhighlight lang=apl inline>⌈</source> Minimum <syntaxhighlight lang=apl inline>⌊</source>

520. Limiting X between Y[1] and Y[2], inclusive <syntaxhighlight lang=apl inline>X←D; Y←D1</source>
<syntaxhighlight lang=apl inline>Y[1]⌈Y[2]⌊X</source>
521. Inserting vector Y to the end of matrix X <syntaxhighlight lang=apl inline>X←A2; Y←A1</source>
<syntaxhighlight lang=apl inline>(A↑X),[⍳1](1↓A←(⍴X)⌈0,⍴Y)↑Y</source>
522. Widening matrix X to be compatible with Y <syntaxhighlight lang=apl inline>X←A2; Y←A2</source>
<syntaxhighlight lang=apl inline>((0 1×⍴Y)⌈⍴X)↑X</source>
523. Lengthening matrix X to be compatible with Y <syntaxhighlight lang=apl inline>X←A2; Y←A2</source>
<syntaxhighlight lang=apl inline>((1 0×⍴Y)⌈⍴X)↑X</source>
524. Reshaping non-empty lower-rank array X into a matrix <syntaxhighlight lang=apl inline>X←A; 2≥⍴⍴X</source>
<syntaxhighlight lang=apl inline>(1⌈¯2↑⍴X)⍴X</source>
525. Take of at most X elements from Y <syntaxhighlight lang=apl inline>X←I; Y←A</source>
<syntaxhighlight lang=apl inline>(X⌊⍴Y)↑Y</source>
526. Limiting indices and giving a default value G <syntaxhighlight lang=apl inline>X←A1; Y←I; G←A0</source>
<syntaxhighlight lang=apl inline>(X,G)[(1+⍴X)⌊Y]</source>

Ceiling <syntaxhighlight lang=apl inline>⌈</source> Floor <syntaxhighlight lang=apl inline>⌊</source>

527. Reshaping X into a matrix of width Y <syntaxhighlight lang=apl inline>X←D, Y←I0</source>
<syntaxhighlight lang=apl inline>((⌈(⍴,X)÷Y),Y)⍴X</source>
528. Rounding to nearest even integer <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>⌊X+1≤2|X</source>
529. Rounding, to nearest even integer for <syntaxhighlight lang=apl inline>.5 = 1 X</source> <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>⌊X+.5×.5≠2|X</source>
530. Rounding, to nearest even integer for <syntaxhighlight lang=apl inline>.5 = 1 X</source> <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>⌊X+.5×.5≠2|X</source>
531. Arithmetic progression from X to Y with step G <syntaxhighlight lang=apl inline>X←D0; Y←D0; G←D0</source>
<syntaxhighlight lang=apl inline>X+(G××Y-X)×(⍳1+|⌊(Y-X)÷G)-⎕IO</source>
532. Centering text line X into a field of width Y <syntaxhighlight lang=apl inline>X←C1; Y←I0</source>
<syntaxhighlight lang=apl inline>(-⌊.5×Y+⍴X)↑X</source>
533. Test if integer <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X=⌊X</source>
534. Rounding currencies to nearest 5 subunits <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>.05×⌊.5+X÷.05</source>
535. First part of numeric code ABBB <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>⌊X÷1000</source>
536. Rounding to X decimals <syntaxhighlight lang=apl inline>X←I; Y←D</source>
<syntaxhighlight lang=apl inline>(10*-X)×⌊0.5+Y×10*X</source>
537. Rounding to nearest hundredth <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>0.01×⌊0.5+100×X</source>
538. Rounding to nearest integer <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>⌊0.5+X</source>
539. Demote floating point representations to integers <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>⌊X</source>

Residue <syntaxhighlight lang=apl inline>|</source>

540. Test if X is a leap year <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>(0=400|X)∨(0≠100|X)∧0=4|X</source>
541. Framing <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>'_',[1]('|',X,'|'),[1]'¯'</source>
542. Magnitude of fractional part <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>1 X</source>
543. Fractional part with sign <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>(×X)|X</source>
544. Increasing the dimension of X to multiple of Y <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>X,(Y|-⍴X)↑0/X</source>
545. Removing every Y:th element of X <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(0≠Y|⍳⍴X)/X</source>
546. Taking every Y:th element of X <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(0=Y|⍳⍴X)/X</source>
547. Divisors of X <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(0=A|X)/A←⍳X</source>
548. Removing every second element of X <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(2|⍳⍴X)/X</source>
549. Elements of X divisible by Y <syntaxhighlight lang=apl inline>X←D1; Y←D0/1</source>
<syntaxhighlight lang=apl inline>(0=Y|X)/X</source>
550. Ravel of a matrix to Y[1] columns with a gap of Y[2] <syntaxhighlight lang=apl inline>X←A2; Y←I1</source>
<syntaxhighlight lang=apl inline>(A×Y[1]*¯1 1)⍴(A←(⍴X)+(Y[1]|-1↑⍴X),Y[2])↑X</source>
551. Test if even <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>~2|X</source>
552. Last part of numeric code ABBB <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>1000|X</source>
553. Fractional part <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>1|X</source>

Magnitude <syntaxhighlight lang=apl inline>|</source>, Signum <syntaxhighlight lang=apl inline>×</source>

554. Increasing absolute value without change of sign <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>(×X)×Y+|X</source>
555. Rounding to zero values of X close to zero <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>X×Y≤|X</source>
556. Square of elements of X without change of sign <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X×|X</source>
557. Choosing according to signum <syntaxhighlight lang=apl inline>X←D; Y←A1</source>
<syntaxhighlight lang=apl inline>Y[2+×X]</source>

Expand <syntaxhighlight lang=apl inline>\</source> <syntaxhighlight lang=apl inline>⍀</source>

558. Not first zero (≤\) in each subvector of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>~(B∧X)∨(B∨X)\A>¯1↓0,A←(B∨X)/B←~Y</source>
559. First one (<\) in each subvector of Y indicated by X <syntaxhighlight lang=apl inline>X←B1; Y←B1</source>
<syntaxhighlight lang=apl inline>(Y∧X)∨(Y∨X)\A>¯1↓0,A←(Y∨X)/Y</source>
560. Replacing elements of X in set Y with blanks/zeroes <syntaxhighlight lang=apl inline>X←A0; Y←A1</source>
<syntaxhighlight lang=apl inline>A\(A←~X∊Y)/X</source>
561. Replacing elements of X not in set Y with blanks/zeroes <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>A\(A←X∊Y)/X</source>
562. Merging X and Y under control of G (mesh) <syntaxhighlight lang=apl inline>X←A1; Y←A1; G←B1</source>
<syntaxhighlight lang=apl inline>A←G\X ⋄ A[(~G)/⍳⍴G]←Y ⋄ A</source>
563. Replacing elements of X not satisfying Y with blanks/zeroes <syntaxhighlight lang=apl inline>X←A; Y←B1</source>
<syntaxhighlight lang=apl inline>Y\Y/X</source>
564. Adding an empty row into X after rows Y <syntaxhighlight lang=apl inline>X←A2; Y←I1</source>
<syntaxhighlight lang=apl inline>(~(⍳(⍴Y)+1⍴⍴X)∊Y+⍳⍴Y)⍀X</source>
565. Test if numeric <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>0∊0\0⍴X</source>
566. Adding an empty row into X after row Y <syntaxhighlight lang=apl inline>X←A2; Y←I0</source>
<syntaxhighlight lang=apl inline>((Y+1)≠⍳1+1⍴⍴X)⍀X</source>
567. Underlining words <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>X,[⎕IO-.1](' '≠X)\'¯'</source>
568. Using boolean matrix Y in expanding X <syntaxhighlight lang=apl inline>X←A1; Y←B2</source>
<syntaxhighlight lang=apl inline>(⍴Y)⍴(,Y)\X</source>
569. Spacing out text <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>((2×⍴X)⍴1 0)\X</source>

Compress <syntaxhighlight lang=apl inline>/</source> <syntaxhighlight lang=apl inline>⌿</source>

570. Lengths of groups of ones in X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>(A>0)/A←(1↓A)-1+¯1↓A←(~A)/⍳⍴A←0,X,0</source>
571. Syllabization of a Finnish word X <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(~A∊1,⍴X)/A←A/⍳⍴A←(1↓A,0)←~X∊'aeiouyÄÖ'</source>
572. Choosing a string according to boolean value G <syntaxhighlight lang=apl inline>X←C1; Y←C1; G←B0</source>
<syntaxhighlight lang=apl inline>(G/X),(~G)/Y</source>
573. Removing leading, multiple and trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(' '=1↑X)↓((1↓A,0)∨A←' '≠X)/X</source>
575. Removing columns Y from array X <syntaxhighlight lang=apl inline>X←A; Y←I1</source>
<syntaxhighlight lang=apl inline>(~(⍳¯1↑⍴X)∊Y)/X</source>
576. Removing trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(¯1↑(' '≠X)/⍳⍴X)⍴X</source>
577. Lengths of subvectors of X having equal elements <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(1↓A)-¯1↓A←(A,1)/⍳1+⍴A←1,(1↓X)≠¯1↓X</source>
578. Field lengths of vector X; G ←→ ending indices <syntaxhighlight lang=apl inline>X←A1; G←I1</source>
<syntaxhighlight lang=apl inline>G-¯1↓0,G←(~⎕IO)+(((1↓X)≠¯1↓X),1)/⍳⍴X</source>
580. Removing multiple and trailing blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>((1↓A,0)∨A←' '≠X)/X</source>
581. Removing leading and multiple blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(A∨¯1↓0,A←' '≠X)/X</source>
582. Removing multiple blanks <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>(A∨¯1↓1,A←' '≠X)/X</source>
583. Removing duplicate Y's from vector X <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>(A∨¯1↓1,A←X≠Y)/X</source>
584. Indices of all occurrences of elements of Y in X <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(X∊Y)/⍳⍴X</source>
585. Union of sets, ? <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>Y,(~X∊Y)/X</source>
586. Elements of X not in Y (difference of sets) <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(~X∊Y)/X</source>
587. Rows of non-empty matrix X starting with a character in Y <syntaxhighlight lang=apl inline>X←A2; Y←A1</source>
<syntaxhighlight lang=apl inline>(X[;1]∊Y)⌿X</source>
588. Intersection of sets, ⍞ <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(X∊Y)/X</source>
589. Reduction with function ⍺ in dimension Y, rank unchanged <syntaxhighlight lang=apl inline>Y←I0; X←A</source>
<syntaxhighlight lang=apl inline>((⍴X)*Y≠⍳⍴⍴X)⍴ ⍺/[Y]X</source>
590. Replacing all values X in G with Y <syntaxhighlight lang=apl inline>X←A0; Y←A0; G←A</source>
<syntaxhighlight lang=apl inline>A[(A=X)/⍳⍴A←,G]←Y ⋄ (⍴G)⍴A</source>
591. Indices of all occurrences of Y in X <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>(Y=X)/⍳⍴X</source>
592. Replacing elements of G satisfying X with Y <syntaxhighlight lang=apl inline>Y←A0; X←B1; G←A1</source>
<syntaxhighlight lang=apl inline>G[X/⍳⍴G]←Y</source>
593. Removing duplicates from positive integers <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>A←9999⍴0 ⋄ A[X]←1 ⋄ A/⍳9999</source>
594. Indices of ones in logical vector X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>X/⍳⍴X</source>
595. Conditional in text <syntaxhighlight lang=apl inline>X←B0</source>
<syntaxhighlight lang=apl inline>((~X)/'IN'),'CORRECT'</source>
596. Removing blanks <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(' '≠X)/X</source>
597. Removing elements Y from vector X <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>(X≠Y)/X</source>
598. Vector to expand a new element after each one in X <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>(,X,[1.5]1)/,X,[1.5]~X</source>
599. Reduction with FUNCTION <syntaxhighlight lang=apl inline>⍺</source> without respect to shape <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>⍺/,X</source>
600. Reshaping scalar X into a one-element vector <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>1/X</source>
601. Empty matrix <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>0⌿X</source>
602. Selecting elements of X satisfying condition Y <syntaxhighlight lang=apl inline>X←A; Y←B1</source>
<syntaxhighlight lang=apl inline>Y/X</source>

Take <syntaxhighlight lang=apl inline>↑</source>

603. Inserting vector X into matrix Y after row G <syntaxhighlight lang=apl inline>X←A1; Y←A2; G←I0</source>
<syntaxhighlight lang=apl inline>Y[⍳G;],[1]((1↓⍴Y)↑X),[1](2↑G)↓Y</source>
604. Filling X with last element of X to length Y <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>Y↑X,Y⍴¯1↑X</source>
605. Input of row Y of text matrix X <syntaxhighlight lang=apl inline>X←C2; Y←I0</source>
<syntaxhighlight lang=apl inline>X[Y;]←(1↑⍴X)↑⍞</source>
606. First ones in groups of ones <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>X>((-⍴⍴X)↑¯1)↓0,X</source>
607. Inserting X into Y after index G <syntaxhighlight lang=apl inline>X←A1; Y←A1; G←I0</source>
<syntaxhighlight lang=apl inline>(G↑Y),X,G↓Y</source>
608. Pairwise differences of successive columns (inverse of +\) <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X-((-⍴⍴X)↑¯1)↓0,X</source>
609. Leftmost neighboring elements <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>((-⍴⍴X)↑¯1)↓0,X</source>
610. Rightmost neighboring elements <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>((-⍴⍴X)↑1)↓X,0</source>
611. Shifting vector X right with Y without rotate <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(-⍴X)↑(-Y)↓X</source>
612. Shifting vector X left with Y without rotate <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(⍴X)↑Y↓X</source>
613. Drop of Y first rows from matrix X <syntaxhighlight lang=apl inline>X←A2; Y←I0</source>
<syntaxhighlight lang=apl inline>(2↑Y)↓X</source>
614. Test if numeric <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>0∊1↑0⍴X</source>
615. Reshaping non-empty lower-rank array X into a matrix <syntaxhighlight lang=apl inline>X←A; 2≥⍴⍴X</source>
<syntaxhighlight lang=apl inline>(¯2↑1 1,⍴X)⍴X</source>
616. Giving a character default value for input <syntaxhighlight lang=apl inline>X←C0</source>
<syntaxhighlight lang=apl inline>1↑⍞,X</source>
617. Adding scalar Y to last element of X <syntaxhighlight lang=apl inline>X←D; Y←D0</source>
<syntaxhighlight lang=apl inline>X+(-⍴X)↑Y</source>
618. Number of rows in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>1↑⍴X</source>
619. Number of columns in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>¯1↑⍴X</source>
620. Ending points for X fields of width Y <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>(X×Y)⍴(-Y)↑1</source>
621. Starting points for X fields of width Y <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>(X×Y)⍴Y↑1</source>
622. Zero or space depending on the type of X (fill element) <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>1↑0⍴X</source>
623. Forming first row of a matrix to be expanded <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>1 80⍴80↑X</source>
624. Vector of length Y with X ones on the left, the rest zeroes <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>Y↑X⍴1</source>
625. Justifying text X to right edge of field of width Y <syntaxhighlight lang=apl inline>Y←I0; X←C1</source>
<syntaxhighlight lang=apl inline>(-Y)↑X</source>

Drop <syntaxhighlight lang=apl inline>↓</source>

627. Starting points of groups of equal elements (non-empty X) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>1,(1↓X)≠¯1↓X</source>
628. Ending points of groups of equal elements (non-empty X) <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>((1↓X)≠¯1↓X),1</source>
629. Pairwise ratios of successive elements of vector X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(1↓X)÷¯1↓X</source>
630. Pairwise differences of successive elements of vector X <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>(1↓X)-¯1↓X</source>
631. Differences of successive elements of X along direction Y <syntaxhighlight lang=apl inline>X←D; Y←I0</source>
<syntaxhighlight lang=apl inline>X-(-Y=⍳⍴⍴X)↓0,[Y]X</source>
632. Ascending series of integers Y..X (for small Y and X) <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>(Y-1)↓⍳X</source>
633. First ones in groups of ones <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>X>¯1↓0,X</source>
634. Last ones in groups of ones <syntaxhighlight lang=apl inline>X←B1</source>
<syntaxhighlight lang=apl inline>X>1↓X,0</source>
635. List of names in X (one per row) <syntaxhighlight lang=apl inline>X←C2</source>
<syntaxhighlight lang=apl inline>1↓,',',X</source>
636. Selection of X or Y depending on condition G <syntaxhighlight lang=apl inline>X←A0; Y←A0; G←B0</source>
<syntaxhighlight lang=apl inline>⍴G↓X,Y</source>
637. Restoring argument of cumulative sum (inverse of +\) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X-¯1↓0,X</source>
638. Drop of Y first rows from matrix X <syntaxhighlight lang=apl inline>X←A2; Y←I0</source>
<syntaxhighlight lang=apl inline>(Y,0)↓X</source>
639. Drop of Y first columns from matrix X <syntaxhighlight lang=apl inline>X←A2; Y←I0</source>
<syntaxhighlight lang=apl inline>(0,Y)↓X</source>
640. Number of rows in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>¯1↓⍴X</source>
641. Number of columns in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>1↓⍴X</source>
642. Conditional drop of Y elements from array X <syntaxhighlight lang=apl inline>X←A; Y←I1; G←B1</source>
<syntaxhighlight lang=apl inline>(Y×G)↓X</source>
643. Conditional drop of last element of X <syntaxhighlight lang=apl inline>X←A1; Y←B0</source>
<syntaxhighlight lang=apl inline>(-Y)↓X</source>

Member Of <syntaxhighlight lang=apl inline>∊</source>

644. Expansion vector with zero after indices Y <syntaxhighlight lang=apl inline>X←A1; Y←I1</source>
<syntaxhighlight lang=apl inline>~(⍳(⍴Y)+⍴X)∊Y+⍳⍴Y</source>
645. Boolean vector of length Y with zeroes in locations X <syntaxhighlight lang=apl inline>X←I; Y←I0</source>
<syntaxhighlight lang=apl inline>(~(⍳Y)∊X)</source>
646. Starting points for X in indices pointed by Y <syntaxhighlight lang=apl inline>X←A1; Y←I1</source>
<syntaxhighlight lang=apl inline>(⍳⍴X)∊Y</source>
647. Boolean vector of length Y with ones in locations X <syntaxhighlight lang=apl inline>X←I; Y←I0</source>
<syntaxhighlight lang=apl inline>(⍳Y)∊X</source>
648. Check for input in range 1..X <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>(Y←⎕)∊⍳X</source>
649. Test if arrays are identical <syntaxhighlight lang=apl inline>X←A; Y←A</source>
<syntaxhighlight lang=apl inline>~0∊X=Y</source>
650. Zeroing elements of Y depending on their values <syntaxhighlight lang=apl inline>Y←D; X←D</source>
<syntaxhighlight lang=apl inline>Y×~Y∊X</source>
651. Test if single or scalar <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>1∊⍴,X</source>
652. Test if vector <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>1∊⍴⍴X</source>
653. Test if X is an empty array <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>0∊⍴X</source>

Index Generator <syntaxhighlight lang=apl inline>⍳</source>

654. Inverting a permutation <syntaxhighlight lang=apl inline>X←I1</source>
<syntaxhighlight lang=apl inline>A←⍳⍴X ⋄ A[X]←A ⋄ A</source>
655. All axes of array X <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⍳⍴⍴X</source>
656. All indices of vector X <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>⍳⍴X</source>
657. Arithmetic progression of Y numbers from X with step G <syntaxhighlight lang=apl inline>X←D0; Y←D0; G←D0</source>
<syntaxhighlight lang=apl inline>X+G×(⍳Y)-⎕IO</source>
658. Consecutive integers from X to Y (arithmetic progression) <syntaxhighlight lang=apl inline>X←I0; Y←I0</source>
<syntaxhighlight lang=apl inline>(X-⎕IO)+⍳1+Y-X</source>
659. Empty numeric vector <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⍳0</source>
660. Index origin (⎕IO) as a vector <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⍳1</source>

Logical Functions <syntaxhighlight lang=apl inline>~</source> <syntaxhighlight lang=apl inline>∨</source> <syntaxhighlight lang=apl inline>∧</source> <syntaxhighlight lang=apl inline>⍱</source> <syntaxhighlight lang=apl inline>⍲</source>

661. Demote non-boolean representations to booleans <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>0∨X</source>
662. Test if X is within range ( Y[1],Y[2] ) <syntaxhighlight lang=apl inline>X←D; Y←D1</source>
<syntaxhighlight lang=apl inline>(Y[1]<X)∧X<Y[2]</source>
663. Test if X is within range [ Y[1],Y[2] ] <syntaxhighlight lang=apl inline>X←D; Y←D1; 2=⍴Y</source>
<syntaxhighlight lang=apl inline>(Y[1]≤X)∧(X≤Y[2])</source>
664. Zeroing all boolean values <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>0∧X</source>
666. Selection of elements of X and Y depending on condition G <syntaxhighlight lang=apl inline>X←D; Y←D; G←B</source>
<syntaxhighlight lang=apl inline>(X×G)+Y×~G</source>
667. Changing an index origin dependent result to be as <syntaxhighlight lang=apl inline>⎕IO=1</source> <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>(~⎕IO)+X</source>
668. Conditional change of elements of Y to one according to X <syntaxhighlight lang=apl inline>Y←D; X←B</source>
<syntaxhighlight lang=apl inline>Y*~X</source>

Comparison <syntaxhighlight lang=apl inline><≤></source> <syntaxhighlight lang=apl inline>≠</source>

669. X implies Y <syntaxhighlight lang=apl inline>X←B; Y←B</source>
<syntaxhighlight lang=apl inline>X≤Y</source>
670. X but not Y <syntaxhighlight lang=apl inline>X←B; Y←B</source>
<syntaxhighlight lang=apl inline>X>Y</source>
671. Avoiding division by zero error (gets value zero) <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>(0≠X)×Y÷X+0=X</source>
672. Exclusive or <syntaxhighlight lang=apl inline>X←B; Y←B</source>
<syntaxhighlight lang=apl inline>X≠Y</source>
673. Replacing zeroes with corresponding elements of Y <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>X+Y×X=0</source>
674. Kronecker delta of X and Y (element of identity matrix) <syntaxhighlight lang=apl inline>X←I; Y←I</source>
<syntaxhighlight lang=apl inline>Y=X</source>

Ravel <syntaxhighlight lang=apl inline>,</source>

675. Catenating Y elements G after every element of X <syntaxhighlight lang=apl inline>X←A1; Y←I0; G←A</source>
<syntaxhighlight lang=apl inline>,X,((⍴X),Y)⍴G</source>
676. Catenating Y elements G before every element of X <syntaxhighlight lang=apl inline>X←A1; Y←I0; G←A0</source>
<syntaxhighlight lang=apl inline>,(((⍴X),Y)⍴G),X</source>
677. Merging vectors X and Y alternately <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>,Y,[⎕IO+.5]X</source>
678. Inserting Y after each element of X <syntaxhighlight lang=apl inline>X←A1; Y←A0</source>
<syntaxhighlight lang=apl inline>,X,[1.1]Y</source>
679. Spacing out text <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>,X,[1.1]' '</source>
680. Reshaping X into a matrix of width Y <syntaxhighlight lang=apl inline>X←D, Y←I0</source>
<syntaxhighlight lang=apl inline>(((⍴,X),1)×Y*¯1 1)⍴X</source>
681. Temporary ravel of X for indexing with G <syntaxhighlight lang=apl inline>X←A; Y←A; G←I</source>
<syntaxhighlight lang=apl inline>A←⍴X ⋄ X←,X ⋄ X[G]←Y ⋄ X←A⍴X</source>
682. Temporary ravel of X for indexing with G <syntaxhighlight lang=apl inline>X←A; Y←A; G←I</source>
<syntaxhighlight lang=apl inline>A←,X ⋄ A[G]←Y ⋄ X←(⍴X)⍴A</source>
683. First column as a matrix <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>X[;,1]</source>
684. Number of elements (also of a scalar) <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⍴,X</source>

Catenate <syntaxhighlight lang=apl inline>,</source>

685. Separating variable length lines <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>X,⎕TC[2],Y</source>
686. X×X identity matrix <syntaxhighlight lang=apl inline>X←I0</source>
<syntaxhighlight lang=apl inline>(X,X)⍴1,X⍴0</source>
687. Array and its negative ('plus minus') <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X,[.5+⍴⍴X]-X</source>
688. Underlining a string <syntaxhighlight lang=apl inline>X←C1</source>
<syntaxhighlight lang=apl inline>X,[⎕IO-.1]'¯'</source>
689. Forming a two-column matrix <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>X,[1.1]Y</source>
690. Forming a two-row matrix <syntaxhighlight lang=apl inline>X←A1; Y←A1</source>
<syntaxhighlight lang=apl inline>X,[.1]Y</source>
691. Selection of X or Y depending on condition G <syntaxhighlight lang=apl inline>X←A0; Y←A0; G←B0</source>
<syntaxhighlight lang=apl inline>(X,Y)[⎕IO+G]</source>
692. Increasing rank of Y to rank of X <syntaxhighlight lang=apl inline>X←A; Y←A</source>
<syntaxhighlight lang=apl inline>((((⍴⍴X)-⍴⍴Y)⍴1),⍴Y)⍴Y</source>
693. Identity matrix of shape of matrix X <syntaxhighlight lang=apl inline>X←D2</source>
<syntaxhighlight lang=apl inline>(⍴X)⍴1,0×X</source>
694. Reshaping vector X into a two-column matrix <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>((0.5×⍴X),2)⍴X</source>
696. Reshaping vector X into a one-row matrix <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>(1,⍴X)⍴X</source>
697. Reshaping vector X into a one-column matrix <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>((⍴X),1)⍴X</source>
698. Forming a Y-row matrix with all rows alike (X) <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(Y,⍴X)⍴X</source>
699. Handling array X temporarily as a vector <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>(⍴X)⍴ ... ,X</source>
700. Joining sentences <syntaxhighlight lang=apl inline>X←A; Y←A1</source>
<syntaxhighlight lang=apl inline>Y,0⍴X</source>
701. Entering from terminal data exceeding input (printing) width <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>X←0 2 1 2 5 8 0 4 5,⎕</source>

Indexing <syntaxhighlight lang=apl inline>[ ]</source>

702. Value of fixed-degree polynomial Y at points X <syntaxhighlight lang=apl inline>Y←D1; X←D</source>
<syntaxhighlight lang=apl inline>Y[3]+X×Y[2]+X×Y[1]</source>
703. Number of columns in array X <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>(⍴X)[⍴⍴X]</source>
704. Number of rows in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(⍴X)[1]</source>
705. Number of columns in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>(⍴X)[2]</source>
706. Conditional elementwise change of sign <syntaxhighlight lang=apl inline>Y←D; X←B</source>
<syntaxhighlight lang=apl inline>Y×(1 ¯1)[1+X]</source>
707. Selection depending on index origin <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>X[2×⎕IO]</source>
708. Indexing with boolean value X (plotting a curve) <syntaxhighlight lang=apl inline>X←B</source>
<syntaxhighlight lang=apl inline>' *'[⎕IO+X]</source>
709. Indexing independent of index origin <syntaxhighlight lang=apl inline>X←A1; Y←I</source>
<syntaxhighlight lang=apl inline>X[⎕IO+Y]</source>
710. Selection depending on index origin <syntaxhighlight lang=apl inline>X←A1</source>
<syntaxhighlight lang=apl inline>X[1]</source>
711. Zeroing a vector (without change of size) <syntaxhighlight lang=apl inline>X←D1</source>
<syntaxhighlight lang=apl inline>X[]←0</source>
712. First column as a vector <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>X[;1]</source>

Shape <syntaxhighlight lang=apl inline>⍴</source>

713. Rank of array X <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⍴⍴X</source>
715. Duplicating vector X Y times <syntaxhighlight lang=apl inline>X←A1; Y←I0</source>
<syntaxhighlight lang=apl inline>(Y×⍴X)⍴X</source>
716. Adding X to each row of Y <syntaxhighlight lang=apl inline>X←D1; Y←D; (⍴X)=¯1↑⍴Y</source>
<syntaxhighlight lang=apl inline>Y+(⍴Y)⍴X</source>
717. Array with shape of Y and X as its rows <syntaxhighlight lang=apl inline>X←A1; Y←A</source>
<syntaxhighlight lang=apl inline>(⍴Y)⍴X</source>
718. Number of rows in matrix X <syntaxhighlight lang=apl inline>X←A2</source>
<syntaxhighlight lang=apl inline>1⍴⍴X</source>

Reshape <syntaxhighlight lang=apl inline>⍴</source>

720. Forming an initially empty array to be expanded <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>0 80⍴0</source>
721. Output of an empty line <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>0⍴X←</source>
722. Reshaping first element of X into a scalar <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⍴X</source>
723. Corner element of a (non-empty) array <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>1⍴X</source>

Arithmetic <syntaxhighlight lang=apl inline>+</source> <syntaxhighlight lang=apl inline>-</source> <syntaxhighlight lang=apl inline>×</source> <syntaxhighlight lang=apl inline>÷</source>

724. Continued fraction <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>1+÷2+÷3+÷4+÷5+÷6+÷ ...</source>
725. Force 0÷0 into DOMAIN ERROR in division <syntaxhighlight lang=apl inline>X←D; Y←D</source>
<syntaxhighlight lang=apl inline>Y×÷X</source>
726. Conditional elementwise change of sign <syntaxhighlight lang=apl inline>X←D; Y←B; ⍴X ←→ ⍴Y</source>
<syntaxhighlight lang=apl inline>Xׯ1*Y</source>
727. Zero array of shape and size of X <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>0×X</source>
728. Selecting elements satisfying condition Y, zeroing others <syntaxhighlight lang=apl inline>X←D; Y←B</source>
<syntaxhighlight lang=apl inline>Y×X</source>
729. Number and its negative ('plus minus') <syntaxhighlight lang=apl inline>X←D0</source>
<syntaxhighlight lang=apl inline>1 ¯1×X</source>
730. Changing an index origin dependent result to be as ⎕IO=0 <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>-⎕IO-X</source>
731. Changing an index origin dependent argument to act as ⎕IO=1 <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>(⎕IO-1)+X</source>
732. Output of assigned numeric value <syntaxhighlight lang=apl inline>X←D</source>
<syntaxhighlight lang=apl inline>+X←</source>
733. Changing an index origin dependent argument to act as ⎕IO=0 <syntaxhighlight lang=apl inline>X←I</source>
<syntaxhighlight lang=apl inline>⎕IO+X</source>
734. Selecting elements satisfying condition Y, others to one <syntaxhighlight lang=apl inline>X←D; Y←B</source>
<syntaxhighlight lang=apl inline>X*Y</source>

Miscellaneous

736. Setting a constant with hyphens <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⎕LX←⍞</source>
737. Output of assigned value <syntaxhighlight lang=apl inline>X←A</source>
<syntaxhighlight lang=apl inline>⎕←X←</source>
738. Syntax error to stop execution <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>*</source>
888. Meaning of life <syntaxhighlight lang=apl inline></source>
<syntaxhighlight lang=apl inline>⍎⊖⍕⊃⊂|⌊-*+○⌈×÷!⌽⍉⌹~⍴⍋⍒,⍟?⍳0</source>

Notes

  1. Note: it doesn't average the middle two elements as per median's definition. A more correct idiomatic expression is <syntaxhighlight lang=apl inline>0.5×+/X[(⍋X)[|⌈¯0.5 0.5×1+⍴X]]</source>