These alternatives ([temp.deduct.call]/4) are considered only if type deduction would otherwise fail. If they yield more than one possible deduced A, the type deduction fails. [ Note: If a template-parameter is not used in any of the function parameters of a function template, or is used only in a non-deduced context, its corresponding template-argument cannot be deduced from a function call and the template-argument must be explicitly specified. — end note ]
My question:
- How these alternative deductions can yield more than one possible "deduced A"?
Please, support the answer with an example that triggers this case.
CodePudding user response：
How these alternative deductions can yield more than one possible "deduced A"? Please, support the answer with an example that triggers this case.
An example of this can be:
template<typename T>
void f(T a, T b)
{
}
int main()
{
f(3, 5.5); //deduced A as int from first deduction while double from second deduction
return 0;
}
Here we have more than one possible "deduced A". From the first argument we've int and from the second argument b we have double.