Preprocessor and template arguments or conditional compilation of piece of code

Question

How I can compile template function with pre-processor condition? Like that (but it is not working):

template 
void f()
{
    #if (var == tru         


        

Answer 1

You can't do that with the preprocessor. All you can do is delegate the code to a separate template, something like this:

template 
void only_if_true()
{}

template <>
void only_if_true()
{
  your_special_code_here();
}


template 
void f()
{
  some_code_always_used();
  only_if_true();
  some_code_always_used();
}

Of course, if you need information shared between f() and only_if_true() (which is likely), you have to pass it as parameters. Or make only_if_true a class and store the shared data in it.