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104 lines
4.8 KiB
HTML
104 lines
4.8 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html>
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<head>
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<title>Arduino - Else </title>
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<link rel='stylesheet' href='arduino.css' type='text/css' />
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<div class="title"><a href="http://www.arduino.cc"/>Arduino</a></div>
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<p><a class='wikilink' href='http://arduino.cc/en/Main/Buy'>Buy</a>
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<a class="urllink" href="http://www.arduino.cc/blog/" rel="nofollow">Blog »</a> |
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<p><strong>Reference</strong> <a class='wikilink' href='index.html'>Language</a> (<a class='wikilink' href='Extended.html'>extended</a>) | <a class='wikilink' href='Libraries.html'>Libraries</a> | <a class='wikilink' href='Comparison.html'>Comparison</a> | <a class='wikilink' href='Changes.html'>Changes</a>
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</p>
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<p class='vspace'></p><h2>if / else</h2>
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<p><strong>if/else</strong> allows greater control over the flow of code than the basic <strong>if</strong> statement, by allowing multiple tests to be grouped together. For example, an analog input could be tested and one action taken if the input was less than 500, and another action taken if the input was 500 or greater. The code would look like this:
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</p>
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<p class='vspace'></p><pre>if (pinFiveInput < 500)
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{
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// action A
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}
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else
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{
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// action B
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}
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</pre>
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<p class='vspace'></p><p><strong>else</strong> can proceed another <strong>if</strong> test, so that multiple, mutually exclusive tests can be run at the same time.
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</p>
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<p class='vspace'></p><p>Each test will proceed to the next one until a true test is encountered. When a true test is found, its associated block of code is run, and the program then skips to the line following the entire if/else construction. If no test proves to be true, the default <strong>else</strong> block is executed, if one is present, and sets the default behavior.
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</p>
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<p class='vspace'></p><p>Note that an <strong>else if</strong> block may be used with or without a terminating <strong>else</strong> block and vice versa. An unlimited number of such <strong>else if</strong> branches is allowed.
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</p>
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<p class='vspace'></p><pre>if (pinFiveInput < 500)
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{
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// do Thing A
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}
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else if (pinFiveInput >= 1000)
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{
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// do Thing B
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}
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else
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{
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// do Thing C
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}
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</pre><p>Another way to express branching, mutually exclusive tests, is with the <a class='wikilink' href='SwitchCase.html'>switch case</a> statement.
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</p>
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<p class='vspace'></p><h4>See also:</h4>
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<p><a class='wikilink' href='SwitchCase.html'>switch case</a>
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</p>
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<p class='vspace'></p><p><a class='wikilink' href='index.html'>Reference Home</a>
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<p class='vspace'></p><p><em>Corrections, suggestions, and new documentation should be posted to the <a class='urllink' href='http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?board=swbugs' rel='nofollow'>Forum</a>.</em>
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</p>
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<p class='vspace'></p><p>The text of the Arduino reference is licensed under a
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<a class='urllink' href='http://creativecommons.org/licenses/by-sa/3.0/' rel='nofollow'>Creative Commons Attribution-ShareAlike 3.0 License</a>. Code samples in the reference are released into the public domain.
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