Re: [Boost-users] function template with a universal reference to a specific type

Subject: Re: [Boost-users] function template with a universal reference to a specific type
From: Ireneusz Szcześniak (irek.szczesniak_at_[hidden])
Date: 2019-01-01 11:09:25

I came up with a solution with a template requirement -- please see 
below.  It works fine with non-templated types (type A below), but not 
with templated types (type B below).

I would appreciate it if someone could help me get it work with 
templated types too.

Best,
Irek

***********************************************************

http://coliru.stacked-crooked.com/a/6219c292938b4067

Compiled with:

g++ -std=c++2a -fconcepts main.cc -o main

***********************************************************

#include <iostream>
#include <type_traits>

using namespace std;

template <typename T>
void
foo(T &&t)
{
   // The primary template implementation.
   cout << "Primary: " << __PRETTY_FUNCTION__ << endl;
}

struct A
{
};

template <typename T>
void
foo(T &&t) requires is_same_v<decay_t<T>, A>
{
   // Overload for A.
   cout << "Overload for A: " << __PRETTY_FUNCTION__ << endl;
}

template <typename T>
struct B
{
};

template <typename T>
void
foo(T &&t) requires is_same_v<decay_t<T>, B>
{
   // Overload for B.
   cout << "Overload for B: " << __PRETTY_FUNCTION__ << endl;
}

int
main()
{
   foo(1);
   int i = 1;
   foo(i);
   const int ci = 1;
   foo(ci);

   foo(A());
   A a;
   foo(a);
   const A ca;
   foo(ca);

   foo(B<int>());
   B<int> b;
   foo(b);
   const B<int> cb;
   foo(cb);
}