Question

I have class Foo with a constructor as given:

class Foo {
 public:
   Foo(int w, char x, int y, int z);
   ...
 };

int main()
{
   Foo abc (10, 'a');
}

Can I use that constructor like this? When constructor signature do not match?

So How do I give default value?

Answer 1

Not unless the parameters at the tail of the signature have defaults, for example:

class Foo {
public:
    Foo(int w, char x, int y=5, int z=0);
    ...
};

If there are defaults, then you can supply only the non-defaulted parameters, and optionally some defaulted ones, i.e. any of the following invocations would be valid:

Foo abc (10, 'a');
Foo abc (10, 'a', 3);
Foo abc (10, 'a', 42, 11);