Question

I currently have a function template, taking a reference, that does something in essence equivalent to:

template <typename T>
void f(T& t)
{
   t = T();
}

Now, I can call:

int a;
f(a);

To initialize my variable a.
I can even do:

std::vector<int> a(10);
f(a[5]);

However, this will fail:

std::vector<bool> a(10);
f(a[5]);

The reason being a[5] returns an object with reference semantic, but not a reference. So I need to be able to write:

template <typename T>
void f(T a)
{
  a = T();
}

But if I add this new template and try to compile the first example (with int), I obtain the following error:

test_multi_tmpl.cc: In function ‘int main()’:
test_multi_tmpl.cc:20: error: call of overloaded ‘f(int&)’ is ambiguous
test_multi_tmpl.cc:6: note: candidates are: void f(T&) [with T = int]
test_multi_tmpl.cc:12: note:                 void f(T) [with T = int]

Any ideas how to solve this? I wouldn’t like to overload f just for std::vector<bool>::reference as this construct might appears in other places …

Answer 1

I think specialising f for std::vector<bool>::reference is your only option.

Note that using std::vector<bool> is probably a bad idea in the first place (the std::vector<bool> specialisation is deprecated for future versions of the c++ language) so you could just use std::deque<bool> instead.