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Prototype: Difference between revisions
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== Examples == | == Examples == | ||
The prototype is used when an array is expanded or when empty elements are inserted in some other way. [[Take]] and [[Expand]] on a [[character]] array produce an array with spaces, because <source lang=apl inline>' '</ | The prototype is used when an array is expanded or when empty elements are inserted in some other way. [[Take]] and [[Expand]] on a [[character]] array produce an array with spaces, because <source lang=apl inline>' '</syntaxhighlight> is the prototype of a character array: | ||
<source lang=apl> | <source lang=apl> | ||
¯12 ↑ 'whitespace' | ¯12 ↑ 'whitespace' | ||
| Line 9: | Line 9: | ||
(5 1 5/1 ¯2 1) \ 'whitespace' | (5 1 5/1 ¯2 1) \ 'whitespace' | ||
white space | white space | ||
</ | </syntaxhighlight> | ||
The [[Rank operator]] combines its left operand's result cells by extending them to a common shape like [[Mix]] does. Numeric vectors of different lengths will be expanded with <source lang=apl inline>0</ | The [[Rank operator]] combines its left operand's result cells by extending them to a common shape like [[Mix]] does. Numeric vectors of different lengths will be expanded with <source lang=apl inline>0</syntaxhighlight>, the prototype for a simple numeric array. | ||
<source lang=apl> | <source lang=apl> | ||
(⍳⍤0) 2 3 4 | (⍳⍤0) 2 3 4 | ||
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1 2 3 0 | 1 2 3 0 | ||
1 2 3 4 | 1 2 3 4 | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]]}} | {{Works in|[[Dyalog APL]]}} | ||
An array's prototype is based on its first element, so the array <source lang=apl inline>a</ | An array's prototype is based on its first element, so the array <source lang=apl inline>a</syntaxhighlight> below has a simple numeric prototype, as does any prefix of <source lang=apl inline>a</syntaxhighlight>. This property even applies to empty arrays: the expression <source lang=apl inline>0 ↑ a</syntaxhighlight> results in an empty array with the same prototype as <source lang=apl inline>a</syntaxhighlight>. | ||
<source lang=apl> | <source lang=apl> | ||
⎕←a ← 5 'c' ¯2 | ⎕←a ← 5 'c' ¯2 | ||
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4 ↑ 0 ↑ a | 4 ↑ 0 ↑ a | ||
0 0 0 0 | 0 0 0 0 | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]]}} | {{Works in|[[Dyalog APL]]}} | ||
| Line 52: | Line 52: | ||
│ │0 0 0│ | │ │0 0 0│ | ||
└──┴─────┘ | └──┴─────┘ | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]]}} | {{Works in|[[Dyalog APL]]}} | ||
| Line 62: | Line 62: | ||
│0│0│ │ | │0│0│ │ | ||
└─┴─┴──┘ | └─┴─┴──┘ | ||
</ | </syntaxhighlight> | ||
{{Works in|[[NARS2000]]}} | {{Works in|[[NARS2000]]}} | ||
<source lang=apl> | <source lang=apl> | ||
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│0│0│ │ | │0│0│ │ | ||
└─┴─┴──┘ | └─┴─┴──┘ | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]] with [[migration level]]<nowiki>=</nowiki>0}} | {{Works in|[[Dyalog APL]] with [[migration level]]<nowiki>=</nowiki>0}} | ||
However, an array's prototype can always be determined by reshaping the array to become empty, and then coercing out a fill element: | However, an array's prototype can always be determined by reshaping the array to become empty, and then coercing out a fill element: | ||
| Line 77: | Line 77: | ||
│0│0│ │ | │0│0│ │ | ||
└─┴─┴──┘ | └─┴─┴──┘ | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]] with [[migration level]]<nowiki>≥</nowiki>2, [[APL2]], [[APLX]]}} | {{Works in|[[Dyalog APL]] with [[migration level]]<nowiki>≥</nowiki>2, [[APL2]], [[APLX]]}} | ||
[https://tryapl.org/?a=%u2283%200%20%u2374%20%281%202%20%27ab%27%29%203%204&run Try it now!] | [https://tryapl.org/?a=%u2283%200%20%u2374%20%281%202%20%27ab%27%29%203%204&run Try it now!] | ||
| Line 85: | Line 85: | ||
│0│0│ │ | │0│0│ │ | ||
└─┴─┴──┘ | └─┴─┴──┘ | ||
</ | </syntaxhighlight> | ||
{{Works in|[[Dyalog APL]] with [[migration level]]<nowiki>=</nowiki>1}} | {{Works in|[[Dyalog APL]] with [[migration level]]<nowiki>=</nowiki>1}} | ||
APLs with a [[flat array model]] do not typically store prototype information, instead using only the array's type ([[character]], [[numeric]], or [[Box|boxed]]) to determine its [[Fill element|fills]]. | APLs with a [[flat array model]] do not typically store prototype information, instead using only the array's type ([[character]], [[numeric]], or [[Box|boxed]]) to determine its [[Fill element|fills]]. | ||
{{APL features}}[[Category:Array relationships]][[Category:Array characteristics]] | {{APL features}}[[Category:Array relationships]][[Category:Array characteristics]] | ||