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| author | Lorry Tar Creator <lorry-tar-importer@baserock.org> | 2009-08-18 20:56:02 +0000 |
|---|---|---|
| committer | Lorry <lorry@roadtrain.codethink.co.uk> | 2012-09-25 16:59:08 +0000 |
| commit | 9f8a09ed743cedd9547bf0661d518647966ab114 (patch) | |
| tree | 9c7803d3b27a8ec22e91792ac7f7932efa128b20 /Examples/python/constants/index.html | |
| download | swig-tarball-master.tar.gz | |
Imported from /srv/lorry/lorry-area/swig-tarball/swig-1.3.40.tar.gz.HEADswig-1.3.40master
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| -rw-r--r-- | Examples/python/constants/index.html | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/Examples/python/constants/index.html b/Examples/python/constants/index.html new file mode 100644 index 0000000..35cc0d7 --- /dev/null +++ b/Examples/python/constants/index.html @@ -0,0 +1,67 @@ +<html> +<head> +<title>SWIG:Examples:python:constants</title> +</head> + +<body bgcolor="#ffffff"> + +<tt>SWIG/Examples/python/constants/</tt> +<hr> + +<H2>Wrapping C Constants</H2> + +<p> +When SWIG encounters C preprocessor macros and C declarations that look like constants, +it creates Python variables 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 Python</h2> + +Click <a href="example.py">here</a> to see a script that prints out the values +of the constants contained in the above file. + +<h2>Key points</h2> + +<ul> +<li>The values of preprocessor macros are converted into Python constants. +<li>Types are inferred by syntax (e.g., "3" is an integer and "3.5" is a float). +<li>Character constants such as 'x' are converted into Python strings. +<li>C string literals such as "Hello World" are converted into Python 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 Python constants. +<li>The Python variables that SWIG creates are not protected from modification. For example, +even if you had this: +<blockquote> +<pre> +#define FOO 73 +</pre> +</blockquote> +a user could come along in a script and type +<blockquote> +<pre> +example.FOO = 13 +</pre> +</blockquote> +Unfortunately, there's no easy way to prevent this. + +<p> +<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> + +<hr> + + +</body> +</html> |