codeblocks-ep/help/html/programmerHelp/make/Foreach-Function.html at master · maifeeulasad/codeblocks-ep · GitHub

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Node:<a name="Foreach%20Function">Foreach Function</a>,
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<h3 class="section">The <code>foreach</code> Function</h3>

   <p>The <code>foreach</code> function is very different from other functions.  It
causes one piece of text to be used repeatedly, each time with a different
substitution performed on it.  It resembles the <code>for</code> command in the
shell <code>sh</code> and the <code>foreach</code> command in the C-shell <code>csh</code>.

   <p>The syntax of the <code>foreach</code> function is:

<pre class="example">     $(foreach <var>var</var>,<var>list</var>,<var>text</var>)
     </pre>

<p>The first two arguments, <var>var</var> and <var>list</var>, are expanded before
anything else is done; note that the last argument, <var>text</var>, is
<strong>not</strong> expanded at the same time.  Then for each word of the expanded
value of <var>list</var>, the variable named by the expanded value of <var>var</var>
is set to that word, and <var>text</var> is expanded.  Presumably <var>text</var>
contains references to that variable, so its expansion will be different
each time.

   <p>The result is that <var>text</var> is expanded as many times as there are
whitespace-separated words in <var>list</var>.  The multiple expansions of
<var>text</var> are concatenated, with spaces between them, to make the result
of <code>foreach</code>.

   <p>This simple example sets the variable <code>files</code> to the list of all files
in the directories in the list <code>dirs</code>:

<pre class="example">     dirs := a b c d
     files := $(foreach dir,$(dirs),$(wildcard $(dir)/*))
     </pre>

   <p>Here <var>text</var> is <code>$(wildcard $(dir)/*)</code>.  The first repetition
finds the value <code>a</code> for <code>dir</code>, so it produces the same result
as <code>$(wildcard a/*)</code>; the second repetition produces the result
of <code>$(wildcard b/*)</code>; and the third, that of <code>$(wildcard c/*)</code>.

   <p>This example has the same result (except for setting <code>dirs</code>) as
the following example:

<pre class="example">     files := $(wildcard a/* b/* c/* d/*)
     </pre>

   <p>When <var>text</var> is complicated, you can improve readability by giving it
a name, with an additional variable:

<pre class="example">     find_files = $(wildcard $(dir)/*)
     dirs := a b c d
     files := $(foreach dir,$(dirs),$(find_files))
     </pre>

<p>Here we use the variable <code>find_files</code> this way.  We use plain <code>=</code>
to define a recursively-expanding variable, so that its value contains an
actual function call to be reexpanded under the control of <code>foreach</code>;
a simply-expanded variable would not do, since <code>wildcard</code> would be
called only once at the time of defining <code>find_files</code>.

   <p>The <code>foreach</code> function has no permanent effect on the variable
<var>var</var>; its value and flavor after the <code>foreach</code> function call are
the same as they were beforehand.  The other values which are taken from
<var>list</var> are in effect only temporarily, during the execution of
<code>foreach</code>.  The variable <var>var</var> is a simply-expanded variable
during the execution of <code>foreach</code>.  If <var>var</var> was undefined
before the <code>foreach</code> function call, it is undefined after the call.
See <a href="Flavors.html#Flavors">The Two Flavors of Variables</a>.

   <p>You must take care when using complex variable expressions that result in
variable names because many strange things are valid variable names, but
are probably not what you intended.  For example,

<pre class="smallexample">     files := $(foreach Esta escrito en espanol!,b c ch,$(find_files))
     </pre>

<p>might be useful if the value of <code>find_files</code> references the variable
whose name is <code>Esta escrito en espanol!</code> (es un nombre bastante largo,
no?), but it is more likely to be a mistake.

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