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'''Split-compose''' is a point-free construct, used to pre-process the argument(s) with the left, and right-most operand before applying the middle operand between the result.
'''Split-compose''' is a point-free construct, used to pre-process it's argument(s) with the left, and right-most operand before applying the middle operand between the result.


It's definition is specified as <source lang=apl inline>(F x) G (H y)</source>.
It's definition is specified as <source lang=apl inline>(F x) G (H y)</source>.

Revision as of 12:34, 12 April 2022

Split-compose is a point-free construct, used to pre-process it's argument(s) with the left, and right-most operand before applying the middle operand between the result.

It's definition is specified as (F x) G (H y).

In BQN, the construct can be formed using Before (⊸) and After (⟜), two compositional operators. In this example, we multiply the range of the left argument, with the absolute value of the right. 

    5 ↕⊸×⟜| 5‿¯8‿¯2‿¯5‿3
⟨ 0 8 4 15 12 ⟩

Monadically, the right argument can be duplicated and split-compose will be applied asymmetrically, similar to hook 

    +´⊸÷⟜≠ ↕10 
⟨ 4.5 ⟩
# This is evaluated as (↕10) +´⊸÷⟜≢ ↕10

Monadically, split-compose is precisely equivalent to a fork. 

    (+´÷≠) ↕10
4.5


In dialects that lack Before, split-compose can be defined differently.

In Dyalog APL you may form the expression with Beside (∘) and Commute (⍨) 

g∘h⍨∘f⍨

g⍨∘f⍨∘h⍨⍨

For example: 

     ÷⍨∘(+/)⍨∘≢⍨⍨ ⍳10
4.5

Whilst these expressions will return the same results (if the functions f,g, & h are pure) the evaluation order is not identical.

And (most commonly) as a fork: 

f⍤⊣ g h⍤⊢

See also


APL syntax [edit]
General Comparison with traditional mathematics ∙ Precedence ∙ Tacit programming (Train, Hook, Split composition)
Array Numeric literal ∙ String ∙ Strand notation ∙ Object literal ∙ Array notation (design considerations)
Function Argument ∙ Function valence ∙ Derived function ∙ Derived operator ∙ Niladic function ∙ Monadic function ∙ Dyadic function ∙ Ambivalent function ∙ Defined function (traditional) ∙ Dfn ∙ Function train
Operator Operand ∙ Operator valence ∙ Tradop ∙ Dop ∙ Derived operator
Assignment Multiple ∙ Indexed ∙ Selective ∙ Modified
Other Function axis ∙ Bracket indexing ∙ Branch ∙ Statement separator ∙ Quad name ∙ System command ∙ User command ∙ Keyword ∙ Dot notation ∙ Function-operator overloading ∙ Control structure ∙ Comment
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