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#REDIRECT ] |
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: ''For its use in ], see ].'' |
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{{Redirect category shell|1= |
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The '''spaceship operator''' is a binary ] that originated in the ] ]. Other languages, such as ] and ] also support the spaceship operator. It is written <code><=></code>. Unlike traditional equality operators, which will return 1 (true) or 0 (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>. |
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{{R to section}} |
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{{R with history}} |
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As a formula: |
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}} |
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:<math> |
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a\ \texttt{<=>}\ b\ \ \ = |
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\begin{cases} |
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-1 & \mbox{if }a < b, \\ |
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0 & \mbox{if }a = b, \\ |
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1 & \mbox{if }a > b, \\ |
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\texttt{undef} |
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& \mbox{otherwise.} |
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\end{cases} |
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</math> |
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The spaceship operator is primarily used for comparisons in ]. |
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The spaceship operator takes its name because it looks like a small ] as ]. The term is now commonly used and the operator is referred by the name within the Perl ]. |
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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. |
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== Example == |
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<source lang="php"> |
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$a = 5 <=> 7; # $a is set to -1 |
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$a = 7 <=> 5; # $a is set to 1 |
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$a = 6 <=> 6; # $a is set to 0 |
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</source> |
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==External links== |
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{{wikibooks|Perl Programming}} |
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* |
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* |
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] |
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