I'm currently playing around using mainline with the variadic template
feature and would like to hear some comments on code gcc is rejecting.
#1:
=====
1 template<typename T, T a, T... Args> T max()
2 {
3 return a > max<T, Args>() ? a : max<T, Args>();
4 };
5
6 template<typename T, T a, T b>T max()
7 {
8 return a > b ? a : b;
9 };
int main()
{
unsigned int a = max<unsigned int, 3, 2>();
unsigned int a = max<unsigned int, 3, 2, 5>();
}
=====
Using the non-variadic template, everything works fine. With the
variadic templates, gcc issues an error in line 3:
error: parameter packs not expanded with `...':
note: 'Args'
I think, that this code is valid. If not, please point it out to me.
#2:
=====
template<template<typename... Params> class Comp, typename... Params>
void f( Params... p)
{
static_assert( Comp<Params>::value, "" );
}
template <typename T>
class Foo
{
static const int value=1;
};
int main()
{
f<Foo, int, int>( );
}
=====
Here I'm not that sure about the validity of the code, my intention was
to use tr1/type_traits in macros on ordinary variables instead of types.
So, the variadic template f would resolve the type for me. That intended
use was something like f<std::tr1::is_same>( _var1, _var2 );, which
would compile-time-check, if _var1 and _var2 are exaclty the same type.
But i'm not even coming that far, as gcc issues: "error: no matching
function for call to 'f()'". Any Ideas, what's wrong here?
