C++ Primer, Fifth Edition

Using auto or decltype for Function Pointer Types

If we know which function(s) we want to return, we can use decltype to simplify writing a function pointer return type. For example, assume we have two functions, both of which return a string::size_type and have two const string& parameters. We can write a third function that takes a string parameter and returns a pointer to one of these two functions as follows:

string::size_type sumLength(const string&, const string&);string::size_type largerLength(const string&, const string&);// depending on the value of its string parameter,// getFcn returns a pointer to sumLength or to largerLengthdecltype(sumLength) *getFcn(const string &);

The only tricky part in declaring getFcn is to remember that when ...