C Primer Plus®, Third Edition

Functions and Pointers

As the discussion on declarations illustrated, it's possible to declare pointers to functions. You might wonder if such a beast has any usefulness. Typically, a function pointer is used as an argument to another function, telling the second function which function to use. For instance, the qsort() function from the C library takes a pointer to a function as one of its arguments. We've used one sorting function for integers and another for strings. The algorithm was the same, but we used > for comparing integers and strcmp() for strings. The qsort() function takes a more general approach. You pass it a pointer to a comparison function appropriate to the type you want to sort, and qsort() then uses that function to sort the ...