| Revision as of 08:55, 21 May 2014 editYatharthROCK (talk | contribs)56 editsm Removed \textt from LaTeX field as it wa erroring out;Tag: Visual edit← Previous edit |
Latest revision as of 19:35, 28 July 2023 edit undoPsychpsyo (talk | contribs)14 editsm Made redirect more specificTag: Redirect target changed |
| (6 intermediate revisions by 5 users not shown) |
| Line 1: |
Line 1: |
|
|
#REDIRECT ] |
|
The '''spaceship operator''', written <code><=></code>, is a binary operator that originated in the ] ]. Other languages, such as ] and ], also support the spaceship operator. Unlike traditional equality operators, which will return true or false depending on whether the arguments are equal or unequal, the spaceship operator will return 1, 0, or −1 depending on the value of the left argument relative to the right argument. If the left argument is greater than the right argument, the operator returns 1. If the left argument is less than the right argument, the operator returns −1. If the two arguments are equal, the operator returns 0. If the two arguments cannot be compared (e.g. one of them is ]), the operator returns <code>undef</code>. |
|
|
|
|
|
|
|
{{Redirect category shell|1= |
|
As a formula: |
|
|
|
{{R to section}} |
|
:<math> |
|
|
|
{{R with history}} |
|
a\ <=>\ b\ \ \ = |
|
|
|
}} |
|
\begin{cases} |
|
|
-1 & \mbox{if }a < b, \\ |
|
|
0 & \mbox{if }a = b, \\ |
|
|
1 & \mbox{if }a > b, \\ |
|
|
undef |
|
|
& \mbox{otherwise.} |
|
|
\end{cases} |
|
|
</math> |
|
|
|
|
|
In Perl, the <code><=></code> operator only performs numeric comparisons. For string-based comparison, the analogous <code>cmp</code> operator is used instead. |
|
|
|
|
|
By allowing any negative number in place of −1 and any positive in place of 1, the <code><=></code> operator can be efficiently implemented for numbers as <code>a - b</code>. |
|
|
|
|
|
The spaceship operator is primarily used for comparisons in ]. |
|
|
|
|
|
The spaceship operator takes its name because it resembles ]'s fighter from ] . The term is now commonly used and the operator is referred by the name within the Perl ]. |
|
|
|
|
|
This operator is also used in ]-based mathematical notation to represent "less than, equal to or greater than", and is synonymous with the symbols {{unicode|⋛}} and {{unicode|⋚}}. It can be used to test if the result of a calculation is actually a number. |
|
|
|
|
|
== Example == |
|
|
<source lang="perl"> |
|
|
$a = 5 <=> 7; # $a is set to -1 |
|
|
$a = 7 <=> 5; # $a is set to 1 |
|
|
$a = 6 <=> 6; # $a is set to 0 |
|
|
</source> |
|
|
|
|
|
== See also == |
|
|
* ] |
|
|
* ] |
|
|
|
|
|
==External links== |
|
|
{{wikibooks|Perl Programming}} |
|
|
* |
|
|
* |
|
|
|
|
|
] |
|
|
] |
|