DUMMY_DEFAULT_ARG.cpp

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// checking for dummy default arguments
 
 
template <class T>
T foo (const T* = 0) { return T (); }
 
template <>
int foo<int>(const int*) { return 1; }
 
template <>
long foo<long>(const long*) { return 2; }
 
 
struct X { };
 
template <class T>
struct A {
    int i_;
 
    A (int i): i_ (i) { }
};
 
template <class T>
struct B {
    int i_;
 
    B (int i): i_ (i) { }
};
 
 
template <class T>
T bar (const X&, const T* = 0) { return T (); }
 
template <>
A<int> bar<A<int> >(const X&, const A<int>*) { return A<int>(1); }
 
template <>
B<long> bar<B<long> >(const X&, const B<long>*) { return B<long>(2); }
 
 
int main ()
{
    int result = 0;
 
    if (0 != foo<char>())
        result = result << 1 + 1;
 
    if (1 != foo<int>())
        result = result << 1 + 1;
 
    if (2 != foo<long>())
        result = result << 1 + 1;
 
    X x;
 
    if (0 != bar<char>(x))
        result = result << 1 + 1;
 
    if (1 != bar<A<int> >(x).i_)
        result = result << 1 + 1;
 
    if (2 != bar<B<long> >(x).i_)
        result = result << 1 + 1;
 
    return result;
}