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git-svn-id: https://swig.svn.sourceforge.net/svnroot/swig/trunk@10005 626c5289-ae23-0410-ae9c-e8d60b6d4f22
52 lines
1.7 KiB
HTML
52 lines
1.7 KiB
HTML
<html>
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<title>SWIG:Examples:java:constants</title>
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</head>
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<body bgcolor="#ffffff">
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<tt>SWIG/Examples/java/constants/</tt>
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<hr>
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<H2>Wrapping C Constants</H2>
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<p>
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When SWIG encounters C preprocessor macros and C declarations that look like constants,
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it creates Java constant with an identical value. Click <a href="example.i">here</a>
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to see a SWIG interface with some constant declarations in it.
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<h2>Accessing Constants from Java</h2>
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Click <a href="../../../Doc/Manual/Java.html#constants">here</a> for the section on constants in the SWIG and Java documentation.
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<p>
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Click <a href="main.java">here</a> to see a Java program that prints out the values
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of the constants contained in the above file.</p>
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<h2>Key points</h2>
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<ul>
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<li>The values of preprocessor macros are converted into Java constants.
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<li>Types are inferred by syntax (e.g., "3" is an integer and "3.5" is a float).
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<li>Character constants such as 'x' are converted into Java strings.
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<li>C string literals such as "Hello World" are converted into Java strings.
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<li>Macros that are not fully defined are simply ignored. For example:
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<blockquote>
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<pre>
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#define EXTERN extern
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</pre>
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</blockquote>
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is ignored because SWIG has no idea what type of variable this would be.
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<p>
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<li>Expressions are allowed provided that all of their components are defined. Otherwise, the constant is ignored.
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<li>Certain C declarations involving 'const' are also turned into Java constants.
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<li>The constants that appear in a SWIG interface file do not have to appear in any sort
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of matching C source file since the creation of a constant does not require linkage
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to a stored value (i.e., a value held in a C global variable or memory location).
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</ul>
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<hr>
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</body>
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</html>
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