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Hi, guys,
I met a issue that compiler can not deduce the template argument type
from my code.


template <typename Precision = float>
struct Vector
{
typedef Precision scalar;

Precision x;

Vector(): x()
{
};

Vector(Precision r)
{
x = r;
}

template <typename P>
Vector(Vector<P>& r)
{
x = (Precision) r.x;
}

template<typename P>
operator P()
{
return (P)x;
};
};

template <typename P>
void Hello(Vector<P> v)
{
};

// use of the template
int main()
{
Hello(1.0f); //Not work

float f;
Hello(f); //Not work

return 0;

}


I want compiler to understand Hello(1.0f) is
Hello( Vector<float>(1.0f) ).
But compiler can't find this.

Hoe can I make implicit constructor of Vector when the argument is
float?

Thanks!

On Aug 14, 2:21 pm, "Alf P. Steinbach" <al...@start.no> wrote:
> * Ed:

> > template <typename P>
> > void Hello(Vector<P> v)
> > {
> > };

> > // use of the template
> > int main()
> > {
> > Hello(1.0f); //Not work

> > float f;
> > Hello(f); //Not work

> > return 0;
> > }

> > I want compiler to understand Hello(1.0f) is
> > Hello( Vector<float>(1.0f) ).
> > But compiler can't find this.

Understandably. A float is not a vector.

> > How can I make implicit constructor of Vector when the
> > argument is float?

> Templated arguments must match *exactly*.

To tell the truth, this has nothing to do with templates. Even
if he had a function "void Hello( Vector<float> v )", it
wouldn't work. (Or maybe it would---he didn't show us the
definition for Vector. But I can't imagine anything called
Vector with a conversion constructor which would take a float.)

--
James Kanze (GABI Software) email:
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