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<a name="The-switch-Statement-1"></a>
<h3 class="section">10.2 The switch Statement</h3>
<a name="index-switch-statement"></a>
<a name="index-case-statement"></a>
<a name="index-otherwise-statement"></a>
<a name="index-endswitch-statement"></a>

<p>It is very common to take different actions depending on the value of
one variable.  This is possible using the <code>if</code> statement in the
following way
</p>
<div class="example">
<pre class="example">if (X == 1)
  do_something ();
elseif (X == 2)
  do_something_else ();
else
  do_something_completely_different ();
endif
</pre></div>

<p>This kind of code can however be very cumbersome to both write and
maintain.  To overcome this problem Octave supports the <code>switch</code>
statement.  Using this statement, the above example becomes
</p>
<div class="example">
<pre class="example">switch (X)
  case 1
    do_something ();
  case 2
    do_something_else ();
  otherwise
    do_something_completely_different ();
endswitch
</pre></div>

<p>This code makes the repetitive structure of the problem more explicit,
making the code easier to read, and hence maintain.  Also, if the
variable <code>X</code> should change its name, only one line would need
changing compared to one line per case when <code>if</code> statements are
used.
</p>
<p>The general form of the <code>switch</code> statement is
</p>
<div class="example">
<pre class="example">switch (<var>expression</var>)
  case <var>label</var>
    <var>command_list</var>
  case <var>label</var>
    <var>command_list</var>
  &hellip;

  otherwise
    <var>command_list</var>
endswitch
</pre></div>

<p>where <var>label</var> can be any expression.  However, duplicate
<var>label</var> values are not detected, and only the <var>command_list</var>
corresponding to the first match will be executed.  For the
<code>switch</code> statement to be meaningful at least one
<code>case <var>label</var> <var>command_list</var></code> clause must be present,
while the <code>otherwise <var>command_list</var></code> clause is optional.
</p>
<p>If <var>label</var> is a cell array the corresponding <var>command_list</var>
is executed if <em>any</em> of the elements of the cell array match
<var>expression</var>.  As an example, the following program will print
&lsquo;<samp>Variable is either 6 or 7</samp>&rsquo;.
</p>
<div class="example">
<pre class="example">A = 7;
switch (A)
  case { 6, 7 }
    printf (&quot;variable is either 6 or 7\n&quot;);
  otherwise
    printf (&quot;variable is neither 6 nor 7\n&quot;);
endswitch
</pre></div>

<p>As with all other specific <code>end</code> keywords, <code>endswitch</code> may be
replaced by <code>end</code>, but you can get better diagnostics if you use
the specific forms.
</p>

<p>One advantage of using the <code>switch</code> statement compared to using
<code>if</code> statements is that the <var>label</var>s can be strings.  If an
<code>if</code> statement is used it is <em>not</em> possible to write
</p>
<div class="example">
<pre class="example">if (X == &quot;a string&quot;) # This is NOT valid
</pre></div>

<p>since a character-to-character comparison between <code>X</code> and the
string will be made instead of evaluating if the strings are equal.
This special-case is handled by the <code>switch</code> statement, and it
is possible to write programs that look like this
</p>
<div class="example">
<pre class="example">switch (X)
  case &quot;a string&quot;
    do_something
  &hellip;
endswitch
</pre></div>

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