redefinition of default argument for class<template-parameter-1-2>

Question

I'm having some issue with the compiler on this SFINAE. Looks like it doesn't resolve the template before raising this error. Here is the code:

template<typename Sig, typename = typename std::enable_if<!std::is_pointer<Sig>::value>::type>
class   GLFunction { /* class def... */ };

template<typename FP, typename = typename std::enable_if<std::is_pointer<FP>::value>::type>
class   GLFunction { /* class def... */ };

Do you know how I can achieve this?

Thx.

Answer 1

Read the error, it tells you what's wrong: you can't redefine a default argument, you must only provide it once.

What are you trying to do? Why have you defined the same template twice? Is one of them meant to be a partial specialization?

Why can't you just do it the simple way, like this?

// Primary template, with default argument:
template <typename Sig, bool = std::is_pointer<Sig>::value>
class   GLFunction { /* class def... */ };

// Partial specialization used for pointers:
template <typename FP>
class   GLFunction<FP, true> { /* class def... */ };