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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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