Finding the Best Match, If Any

The third step of function matching determines which viable function provides the best match for the call. This process looks at each argument in the call and selects the viable function (or functions) for which the corresponding parameter best matches the argument. We’ll explain the details of “best” in the next section, but the idea is that the closer the types of the argument and parameter are to each other, the better the match.

In our case, there is only one (explicit) argument in the call. That argument has type double. To call f(int), the argument would have to be converted from double to int. The other viable function, f(double, double), is an exact match for this argument. An exact match is better than a match that requires a conversion. Therefore, the compiler will resolve the call f(5.6) as a call to the function that has two double parameters. The compiler will add the default argument for the second, missing argument.