C++ Primer Plus

Predefined Functors

The STL defines several elementary functors. They perform actions such as adding two values and comparing two values for equality. They are provided to help support STL functions that take functions as arguments. For example, consider the transform() function. It has two versions. The first version takes four arguments. The first two arguments are iterators that specify a range in a container. (By now you must be familiar with that approach.) The third is an iterator that specifies where to copy the result. The final is a functor that is applied to each element in the range to produce each new element in the result. For example, consider the following:

const int LIM = 5;double arr1[LIM] = {36, 39, 42, 45, 48};vector<double> ...