Two conditions for template function parameters to be specified

1. When the parameter deduction fails, ambiguous is generated. You can understand the specified parameter.

Min5 <double> (dobj, fobj );

2. When the compiler cannot push the returned type

Template <class T1, class T2, class T3>

T1 sum (T2, T3 );

When a parameter is specified, only parameters at the end can be left blank, for example:

Sum <double> (fobj, dobj); // The Return Value Type T1 is double, T2 is float, and T3 is double

Sum <double, double> (fobj, dobj); // error. Only the following