std::fill() and std::fill_n() work similarly but differ in the way the range is specified: for the former by a first and last iterator, for the latter by a first iterator and a count. The second algorithm returns an iterator, representing either the one-past-last assigned element if the counter is greater than zero, or an iterator to the first element of the range otherwise.

std::generate() and std::generate_n() are also similar, differing only in the way the range is specified. The first takes two iterators, defining the range's lower and upper bounds, and the second, an iterator to the first element and a count. Like std::fill_n(), std::generate_n() also returns an iterator, representing either the one-past-last assigned element if the count is greater than zero, or an iterator to the first element of the range, otherwise. These algorithms call a specified function for each element in the range and assign the returned value to the element. The generating function does not take any argument, so the value of the argument cannot be passed to the function as this is intended as a function to initialize the elements of a range. If you need to use the value of the elements to generate new values, you should use std::transform().

std::iota() takes its name from the ι (iota) function from the APL programming language, and though it was a part of the initial STL, it was only included in the standard library in C++11. This function takes a first and last iterator to a range and an initial value that is assigned to the first element of the range and then used to generate sequentially increasing values using the prefix operator++ for the rest of the elements in the range.