Re: What's wrong with this code?
shri314@gmail.com wrote:
template <class T>
struct A
{
template<class U>
A(int, long)
{
}
};
int main()
{
A<int> a(2, 3L);
}
Question: what is 'U' in the above constructor call? If you can't tell, how
should the compiler?
I don't really understand why this should not work. Is it really
necessary for typename U to play a role to select the correct
constructor?
No, generally not. However, if the type can not be inferred from the
parameters, it must be given explicitly. I haven't tested it, but I would
try
A<int> a<...>(2, 3L);
...of course substituting '...' with some type.
Notes:
1. I don't think it matters in any way that A itself is a template, only
that the constructor is one.
2. The above solution sure works for a function:
template<typename T> T default_value() { return T(); }
// doesn't compile, T is unknown
default_value();
// works
default_value<float>();
Uli
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