why we need type casting for float in function overloading

The function was like

Code:

class calc
{
float area(float a)
{
    return a*a;
}
int area(int a)
{
return a*a;
}
};
main()
{
calc ob1;
ob1.area(10);
ob1.area(10.5);
getch();
}

 

Because

Code:

int foo(int bar)
{
...
}

int quux()
{
  foo(10.5);
}

is legal, so the compiler doesn't know if the second call to area() is to area(int(10.5)) or area(float). The cast removes the ambiguity.