Ellipsis (computer programming): Difference between revisions

Revision as of 15:38, 18 December 2019

Revision as of 17:43, 11 May 2020

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The [[GNU Compiler Collection]] has an extension to the C and C++ language to allow ''case ranges'' in [[switch statement]]s:

<sourcesyntaxhighlight lang="C">

switch(u) {

case 0 ... 0x7F : putchar(c); break;

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default: error("not supported!");

}

</syntaxhighlight>

</source>

Delphi / Turbo Pascal / Free Pascal:

<sourcesyntaxhighlight lang="delphi">

var FilteredChars: set of [#0..#32,#127,'a'..'z'];

var CheckedItems: set of [4,10..38,241,58];

</syntaxhighlight>

</source>

In the [[Unified Modeling Language]] (UML), a two-character ellipsis is used to indicate variable cardinality of an association. For example, a cardinality of 1..* means that the number of elements aggregated in an association can range from 1 to infinity (a usage equivalent to [[Kleene plus]]).

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PHP 5.6 supports<ref>https://wiki.php.net/rfc/variadics</ref> use of ellipsis to define an explicitly [[variadic function]], where <code>...</code> before an argument in a function definition means that arguments from that point on will be collected into an array. For example:

<sourcesyntaxhighlight lang="php">

function variadic_function($a, $b, ...$other)

{

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var_dump(variadic_function(1, 2, 3, 4, 5));

</syntaxhighlight>

</source>

Produces this output:

<sourcesyntaxhighlight lang="php">

array(3) {

[0]=>

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int(5)

}

</syntaxhighlight>

</source>

== Multiple dimensions ==

In [[Python (programming language)|Python]], particularly in [[numpy]], an ellipsis is used for slicing an arbitrary number of dimensions for a high-dimensional array:<ref>http://docs.scipy.org/doc/numpy/reference/arrays.indexing.html</ref>

<sourcesyntaxhighlight lang="numpy">

>>> import numpy as np

>>> t = np.random.rand(2, 3, 4, 5)

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>>> t[0, ...].shape # select 1st element from first dimension, copy rest

(3, 4, 5)

</syntaxhighlight>

</source>

== Other semantics ==