2.3 Template Parameters

So far, we have looked at cases in which either all or none of the function template arguments were mentioned explicitly. Another approach is to specify only the first arguments explicitly and to allow the deduction process to derive the rest. In general, you must specify all the argument types up to the last argument type that cannot be determined implicitly. Thus, if you change the order of the template parameters in our example, the caller needs to specify only the return type:

template <typename RT, typename T1, typename T2> 
inline RT max (T1 const& a, T2 const& b); 
… 
max<double>(4,4.2)    // OK: return type is double

In this example, the call to max<double> explicitly sets RT to double, but the parameters T1 and T2 are deduced to be int and double from the arguments.