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How I can compile template function with pre-processor condition? Like that (but it is not working):
template <bool var>
void f()
{
#if (var == true)
// ...
#endif
}
764
Conditional compilation provides a way of including or omitting selected lines of source code depending on the values of literals specified by the DEFINE directive. In this way, you can create multiple variants of the same program without the need to maintain separate source streams.
Compiler creates a new instance of a template function for every data type. So compiler creates two functions in the above example, one for int and other for double. Every instance has its own copy of static variable. The int instance of function is called twice, so count is incremented for the second call.
In other words, a template is a mechanism that allows a programmer to use types as parameters for a class or a function. The compiler then generates a specific class or function when we later provide specific types as arguments.
You can't. The preprocessor, as this names indicates, processes the source file before the compiler. It has therefore no knowledge of the values of your template arguments.
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