Case: Difference between revisions

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{{Built-in|Case|%}}, or '''Merge''', is a [[dyadic]] [[primitive]] function in [[Kap]] and [[dzaima/APL]] that forms an array by mixing [[element]]s taken from a [[vector]] of arrays according to an array of [[index|indices]]. It's closely related to the [[J]] adverb ([[monadic operator]]) Composite Item <syntaxhighlight lang=j inline>}</syntaxhighlight>, which differs in that the right argument is an array whose [[major cell]]s are mixed together. It can also be considered a generalization of a blend instruction in [[wikipedia:SIMD|SIMD]] programming, which chooses between two arguments based on a boolean mask, an operation that might be written <syntaxhighlight lang=apl inline>(A∧~M)∨(B∧M)</syntaxhighlight> in APL.
{{Built-in|Case|%}}, or '''Merge''', is a [[dyadic]] [[primitive]] function in [[Kap]] and [[dzaima/APL]] that forms an array by mixing [[element]]s taken from a [[vector]] of arrays according to an array of [[index|indices]]. It's closely related to the [[J]] adverb ([[monadic operator]]) Composite Item <syntaxhighlight lang=j inline>}</syntaxhighlight>, which differs in that the right argument is an array whose [[major cell]]s are mixed together. It can also be considered a generalization of [[Mask]], which chooses between two arguments based on a boolean mask and might be implemented as <syntaxhighlight lang=apl inline>(A∧~M)∨(B∧M)</syntaxhighlight>.


The following example shows how Case may be used to mix three vectors together:
The following example shows how Case may be used to mix three vectors together:

Latest revision as of 02:25, 9 March 2024

%

Case (%), or Merge, is a dyadic primitive function in Kap and dzaima/APL that forms an array by mixing elements taken from a vector of arrays according to an array of indices. It's closely related to the J adverb (monadic operator) Composite Item }, which differs in that the right argument is an array whose major cells are mixed together. It can also be considered a generalization of Mask, which chooses between two arguments based on a boolean mask and might be implemented as (A∧~M)∨(B∧M).

The following example shows how Case may be used to mix three vectors together: 

      3 2 1 2 3 % 'abcde' 'ABCDE' '01234'
0BcD4
Works in: dzaima/APL

The right argument is a vector of arrays all of the same shape, and the left argument is a simple numeric array with the same shape as each element of the right argument as well as the result. The result value at a given position is taken from the same position in the i'th right argument array, where i is the index at that position in the left argument.

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
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
Dyadic Bind ∙ Compositions (Compose, Reverse Compose, Beside, Withe, Atop, Over) ∙ Inner Product ∙ Determinant ∙ Power ∙ At ∙ Under ∙ Rank ∙ Depth ∙ Variant ∙ Stencil ∙ Cut ∙ Direct definition (operator)
Quad names Index origin ∙ Comparison tolerance ∙ Migration level ∙ Atomic vector
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