Empty array: Difference between revisions
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→Empty array prototype
Miraheze>Adám Brudzewsky |
Miraheze>Adám Brudzewsky |
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{{Works in|[[Dyalog APL]]}} | {{Works in|[[Dyalog APL]]}} | ||
== Reduction over a length-0 axis == | |||
If a [[reduce|reduction]] (using one of <source lang=apl inline>/</source>, <source lang=apl inline>⌿</source>, <source lang=apl inline>\</source>, or <source lang=apl inline>⍀</source>)is performed over an axis of length 0, the resulting array is filled with [[identity element]]s. For example, the sum of an empty list is 0 because the identity element for [[addition]] is 0: | |||
<source lang=apl> | |||
+/0⍴0 | |||
0 | |||
</source> | |||
The identity element for a specific reduction always depends on the operand, and may depend on the argument array prototype. Dialects differ in their support for such reductions. All define identity elements for most [[scalar functions#Standard scalar functions|scalar primitives]], and some stop there (e.g. [[SAX]]), while others (e.g. [[Dyalog APL]] and [[APL2]]) define identity elements for various [[mixed functions]]. | |||
{{APL programming language}} | {{APL programming language}} | ||