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 3<title>SWIG:Examples:java:constants</title>
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 8<tt>SWIG/Examples/java/constants/</tt>
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10
11<H2>Wrapping C Constants</H2>
12
13<tt>$Header$</tt><br>
14
15<p>
16When SWIG encounters C preprocessor macros and C declarations that look like constants,
17it creates Java constant with an identical value.  Click <a href="example.i">here</a>
18to see a SWIG interface with some constant declarations in it.
19
20<h2>Accessing Constants from Java</h2>
21
22Click <a href="main.java">here</a> to see a Java program that prints out the values
23of the constants contained in the above file.
24
25<h2>Key points</h2>
26
27<ul>
28<li>The values of preprocessor macros are converted into Java constants.
29<li>Types are inferred by syntax (e.g., "3" is an integer and "3.5" is a float).
30<li>Character constants such as 'x' are converted into Java strings.
31<li>C string literals such as "Hello World" are converted into Java strings.
32<li>Macros that are not fully defined are simply ignored.  For example:
33<blockquote>
34<pre>
35#define EXTERN extern
36</pre>
37</blockquote>
38is ignored because SWIG has no idea what type of variable this would be.
39
40<p>
41<li>Expressions are allowed provided that all of their components are defined. Otherwise, the constant is ignored.
42
43<li>Certain C declarations involving 'const' are also turned into Java constants. 
44<li>The constants that appear in a SWIG interface file do not have to appear in any sort
45of matching C source file since the creation of a constant does not require linkage
46to a stored value (i.e., a value held in a C global variable or memory location).
47</ul>
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