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Split composition: Difference between revisions
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'''Split composition''' is a [[tacit]] pattern, used to pre-process argument(s) with the outer-most operands before applying the middle operand between the result. Given functions <syntaxhighlight lang=apl inline>f</syntaxhighlight>, <syntaxhighlight lang=apl inline>g</syntaxhighlight>, and <syntaxhighlight lang=apl inline>h</syntaxhighlight>, a split composition on arguments <syntaxhighlight lang=apl inline>x</syntaxhighlight> and <syntaxhighlight lang=apl inline>y</syntaxhighlight> is defined as <syntaxhighlight lang=apl inline>(f x) g (h y)</syntaxhighlight>. | '''Split composition''' is a [[tacit]] pattern, used to pre-process argument(s) with the outer-most operands before applying the middle operand between the result. Given functions <syntaxhighlight lang=apl inline>f</syntaxhighlight>, <syntaxhighlight lang=apl inline>g</syntaxhighlight>, and <syntaxhighlight lang=apl inline>h</syntaxhighlight>, a split composition on arguments <syntaxhighlight lang=apl inline>x</syntaxhighlight> and <syntaxhighlight lang=apl inline>y</syntaxhighlight> is defined as <syntaxhighlight lang=apl inline>(f x) g (h y)</syntaxhighlight>. | ||
This construct was introduced by the [[I|I language]] as "split-compose", where it is represented with <syntaxhighlight lang=apl inline>O</syntaxhighlight> | This construct was introduced by the [[I|I language]] as "split-compose", where it is represented with <syntaxhighlight lang=apl inline>O</syntaxhighlight> which also represents the [[Over]] operator - as it too is a split composition with identical outer operands. | ||
This doesn't appear as a primitive in any APL, nor can it, because it [[composition|composes]] three functions, while a [[Function composition|compositional operator]] can take no more than two [[operands]]. This situation is identical to that of the [[fork]]. Both split compositions and forks can be constructed using companion operators, tying together the three involved functions. | This doesn't appear as a primitive in any APL, nor can it, because it [[composition|composes]] three functions, while a [[Function composition|compositional operator]] can take no more than two [[operands]]. This situation is identical to that of the [[fork]]. Both split compositions and forks can be constructed using companion operators, tying together the three involved functions. | ||