Question

Let say, that i have defined the same function for windows and mac, with different return values like this:

#ifdef _WIN32

// Windows code
int porting(int input){
  return input + 360;
}

#endif

#ifdef __APPLE__

// Mac code
int porting(int input){
  return input + 180;
}

#endif

Is there a way to allow the user to specify code to run inside porting(), instead of having multiple definitions?

Answer 1

C++, as a compiled language, has no eval() function, which many interpreted languages (such as PHP or Javascript) have. There is no way to execute textual user-supplied code at runtime.

Perhaps a callback would suffice for your needs?

Example:

typedef int (*userfunction)(int);

userfunction thefunction;

void set_user_function(userfunction uf)
{
    thefunction = uf;
}

int porting(int input)
{
    return thefunction(input);
}