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1<html> 2<head> 3<title>SWIG:Examples:java:constants</title> 4</head> 5 6<body bgcolor="#ffffff"> 7 8<tt>SWIG/Examples/java/constants/</tt> 9<hr> 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> 48 49<hr> 50 51 52</body> 53</html>