CODEWITHSUNDEEP
c++macros
Deepak Kiran
Deepak Kiran

Reputation: 317

Using user defined math functions when compiled with a macro, or simply use the function from a standard math library in c++

I have my own implementation of a f_sin(x) function,(analogous implementation to sin(x) in ) that I want to use when compiled with a macro named MYMATH. If the MYMATH is not defined I want to use the function sin(x) from the math.h

Any leads on how to go about?

Note I cannot change anything in the function definitions of f_sin(x) or sin(x).

Upvotes: 1

Views: 338

Answers (2)

Gerard097
Gerard097

Reputation: 815

You can try using a macro for each function and then just define it depending on your macro MYMATH. Also if you prefer avoiding this kind of macros you can use a generic lambda as a wrapper.

MyMath.hpp

1.- With Macros for each function

#ifdef MYMATH
#define imp_sin(x) f_sin(x)
#else
#include <cmath>
#define imp_sin(x) std::sin(x)
#endif

2. With generic lambda (C++ 14)

#define glambda(x) [](auto y){ return x(y); }
#ifdef MYMATH
auto imp_sin = glambda(f_sin);
#else
#include <cmath>
auto imp_sin = glambda(std::sin);
#endif
#undef glambda //Or not if you want to keep this helper

Usage main.cpp

#include "MyMath.hpp"
int main(int, char**) {
  imp_sin(3.4f);
  return 0;
}

Upvotes: 1

463035818_is_not_an_ai
463035818_is_not_an_ai

Reputation: 122460

You can do it like this:

double sin_wrapper(double x) {    
#ifdef MYMATH
    return f_sin(x);
#else
    return std::sin(x);
#endif
}

and then replace all calls to sin with calls to this wrapper.

Upvotes: 3

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