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<title>SWIG:Examples:go:constants</title>
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<tt>SWIG/Examples/go/constants/</tt>
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<H2>Wrapping C Constants</H2>

<p>
When SWIG encounters C preprocessor macros and C declarations that
look like constants, it creates a Go constant with an identical value.
Click <a href="example.i">here</a> to see a SWIG interface with some
constant declarations in it.


<h2>Accessing Constants from Go</h2>
Click <a href="../../../Doc/Manual/Go.html#go_constants">here</a> for
the section on constants in the SWIG and Go documentation.
<p>

Click <a href="runme.go">here</a> to see a Go program that prints out
the values of the constants contained in the above file.</p>
<h2>Key points</h2>
<ul>
<li>All names are capitalized to make them visible.
<li>The values of preprocessor macros are converted into Go constants.
<li>C string literals such as "Hello World" are converted into Go strings.
<li>Macros that are not fully defined are simply ignored.  For example:
<blockquote>
<pre>
#define EXTERN extern
</pre>
</blockquote>
is ignored because SWIG has no idea what type of variable this would be.

<p>
<li>Expressions are allowed provided that all of their components are
defined. Otherwise, the constant is ignored.

<li>Certain C declarations involving 'const' are also turned into Go
constants.
<li>The constants that appear in a SWIG interface file do not have to
appear in any sort of matching C source file since the creation of a
constant does not require linkage to a stored value (i.e., a value
held in a C global variable or memory location).
</ul>

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