Commute: Difference between revisions

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{{Built-in|Commute|⍨}} is a [[Primitive function|primitive]] [[monadic]] [[operator]] that takes a [[function]] on its left and returns a new function with swapped arguments.
{{Built-in|Commute|⍨}} is a [[monadic operator]] that takes a [[[dyadic function]] as operand and modifies how the argument(s) of its derived functions are used. If the derived function is used monadically, the argument is also used as left argument. This usage is also known as '''Self''' or, more informally, '''Selfie'''. If the derived function is used dyadically, the arguments are swapped. This usage is also known as '''Swap'''.


== Examples ==
== Examples ==


Subtract one from every item of the input array.
This decrements from the vector:
<source lang=apl>
<source lang=apl>
1 -⍨ 1 2 3
      1 -⍨ 1 2 3
0 1 2
</source>
</source>
{{Works in|[[Dyalog APL]], [[dzaima/APL]], [[NARS2000]]}}
Double:
<source lang=apl>
      +⍨1 2 3
2 4 6
</source>
{{Works in|[[Dyalog APL]], [[dzaima/APL]], [[NARS2000]]}}


== External links ==
== External links ==
Line 12: Line 20:
=== Lessons ===
=== Lessons ===


* [https://chat.stackexchange.com/transcript/52405?m=40900200#40900200 APL Cultivation]
* [https://chat.stackexchange.com/rooms/52405/conversation/lesson-3-some-apl-operators-----#40900200]


=== Documentation ===
=== Documentation ===

Revision as of 15:04, 26 April 2020

⍨

Commute (⍨) is a monadic operator that takes a [[[dyadic function]] as operand and modifies how the argument(s) of its derived functions are used. If the derived function is used monadically, the argument is also used as left argument. This usage is also known as Self or, more informally, Selfie. If the derived function is used dyadically, the arguments are swapped. This usage is also known as Swap.

Examples

This decrements from the vector: 

      1 -⍨ 1 2 3
0 1 2
Works in: Dyalog APL, dzaima/APL, NARS2000

Double: 

      +⍨1 2 3
2 4 6
Works in: Dyalog APL, dzaima/APL, NARS2000

External links

Lessons

Documentation


APL built-ins [edit]
Primitives (Timeline) Functions
Scalar
Monadic Conjugate ∙ Negate ∙ Signum ∙ Reciprocal ∙ Magnitude ∙ Exponential ∙ Natural Logarithm ∙ Floor ∙ Ceiling ∙ Factorial ∙ Not ∙ Pi Times ∙ Roll ∙ Type ∙ Imaginary ∙ Square Root ∙ Round
Dyadic Add ∙ Subtract ∙ Times ∙ Divide ∙ Residue ∙ Power ∙ Logarithm ∙ Minimum ∙ Maximum ∙ Binomial ∙ Comparison functions ∙ Boolean functions (And, Or, Nand, Nor) ∙ GCD ∙ LCM ∙ Circular ∙ Complex ∙ Root
Non-Scalar
Structural Shape ∙ Reshape ∙ Tally ∙ Depth ∙ Ravel ∙ Enlist ∙ Table ∙ Catenate ∙ Reverse ∙ Rotate ∙ Transpose ∙ Raze ∙ Mix ∙ Split ∙ Enclose ∙ Nest ∙ Cut (K) ∙ Pair ∙ Link ∙ Partitioned Enclose ∙ Partition
Selection First ∙ Pick ∙ Take ∙ Drop ∙ Unique ∙ Identity ∙ Stop ∙ Select ∙ Replicate ∙ Expand ∙ Set functions (Intersection ∙ Union ∙ Without) ∙ Bracket indexing ∙ Index ∙ Cartesian Product ∙ Sort
Selector Index generator ∙ Grade ∙ Index Of ∙ Interval Index ∙ Indices ∙ Deal ∙ Prefix and suffix vectors
Computational Match ∙ Not Match ∙ Membership ∙ Find ∙ Nub Sieve ∙ Encode ∙ Decode ∙ Matrix Inverse ∙ Matrix Divide ∙ Format ∙ Execute ∙ Materialise ∙ Range
Operators Monadic Each ∙ Commute ∙ Constant ∙ Replicate ∙ Expand ∙ Reduce ∙ Windowed Reduce ∙ Scan ∙ Outer Product ∙ Key ∙ I-Beam ∙ Spawn ∙ Function axis ∙ Identity (Null, Ident)
Dyadic Bind ∙ Compositions (Compose, Reverse Compose, Beside, Withe, Atop, Over) ∙ Inner Product ∙ Determinant ∙ Power ∙ At ∙ Under ∙ Rank ∙ Depth ∙ Variant ∙ Stencil ∙ Cut ∙ Direct definition (operator) ∙ Identity (Lev, Dex)
Quad names Index origin ∙ Comparison tolerance ∙ Migration level ∙ Atomic vector
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