2,954
edits
Conformability: Difference between revisions
Jump to navigation
Jump to search
→Frame conformability: NARS2000 has singleton extension for frame conformability
Miraheze>Adám Brudzewsky m (Text replacement - "{{APL programming language}}" to "{{APL features}}") |
(→Frame conformability: NARS2000 has singleton extension for frame conformability) |
||
| (10 intermediate revisions by 3 users not shown) | |||
| Line 1: | Line 1: | ||
'''Conformability''' describes the conditions that must be satisfied by [[argument]]s to [[dyadic]] [[scalar function]]s. The arguments must match in [[shape]], taking into account [[scalar extension]] and, when | '''Conformability''' describes the conditions that must be satisfied by [[argument]]s to [[dyadic]] [[scalar function]]s. The arguments must match in [[shape]], taking into account [[scalar extension]] and, when supported, [[singleton extension]] or [[leading axis agreement]]. The criteria which determine the result shape are often considered part of conformability as well. The [[Each]] operator also checks conformability when called dyadically, and some functionality, such as [[multiple assignment]], might use modified conformability rules. | ||
Two arguments are said to conform when | Two arguments are said to conform when they have matching shapes, or one of them is extendible to match the other's shape. Possible rules for extensibility are: | ||
* [[Scalar extension]]: one argument is a [[scalar]] (this is used in all APLs). | |||
* [[Singleton extension]]: at least one argument is a [[singleton]]. | |||
* [[Leading axis agreement]]: one argument's shape is a [[prefix]] of the other's. This is a superset of scalar extension. | |||
The result shape associated with such arguments can then be determined: | The result shape associated with such arguments can then be determined: | ||
| Line 10: | Line 11: | ||
* Otherwise, it is the shape of the argument with the largest rank (this condition is only possible with [[singleton extension]]). | * Otherwise, it is the shape of the argument with the largest rank (this condition is only possible with [[singleton extension]]). | ||
== Frame conformability == | |||
{{APL features}} | {{main|Frame agreement}} | ||
The [[Rank operator]] and [[function rank]] check for conformability not on the entire [[shape]]s of arguments, but only on their [[frame]]s. The same procedure applies to determine whether two frames conform, and if function <syntaxhighlight lang=apl inline>f</syntaxhighlight>'s result shape is known, then the result shape of <syntaxhighlight lang=apl inline>f⍤l r</syntaxhighlight> can be found by appending it to the shape obtained from conformability on the frames computed from [[Rank (operator)|ranks]] <syntaxhighlight lang=apl inline>l</syntaxhighlight> and <syntaxhighlight lang=apl inline>r</syntaxhighlight>. Rather than copying [[element]]s of the extended argument to match the other one, [[cell]]s are copied. | |||
Frame conformability may not allow [[singleton extension]] even when ordinary conformability supports it: [[Dyalog APL]], [[SHARP APL]], and [[A+]] have singleton extension for scalar dyadics but not for Rank (and [[J]] doesn't implement singleton extension). Of these, [[J]] and [[A+]] use [[leading axis agreement]] while SHARP and Dyalog use only empty-frame extension, the equivalent of scalar extension. However, [[NARS2000]] implements Rank with singleton extension for frames. | |||
== External links == | |||
* [https://forums.dyalog.com/viewtopic.php?f=30&t=1621 Scalar functions] and [https://forums.dyalog.com/viewtopic.php?f=30&t=1622 Tally and scalar functions] by [[Roger Hui]] | |||
{{APL features}}[[Category:Function characteristics]][[Category:Conformability]] | |||