Svenska städer

generate


Category: algorithms	Component type: function

Prototype

template <class ForwardIterator, class Generator>
void generate(ForwardIterator first, ForwardIterator last, Generator gen);

Description

Generate assigns the result of invoking gen, a function object that takes no arguments, to each element in the range [first, last). [1]

Definition

Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

Requirements on types

ForwardIterator is a model of Forward Iterator. [2]
ForwardIterator is mutable.
Generator is a model of Generator.
Generator's result type is convertible to ForwardIterator's value type.

Preconditions

[first, last) is a valid range.

Complexity

Linear. Exactly last - first invocations of gen. [1]

Example

Fill a vector with random numbers, using the standard C library function rand.

vector<int> V;
...
generate(V.begin(), V.end(), rand);

Notes

[1] The function object gen is invoked for each iterator in the range [first, last), as opposed to just being invoked a single time outside the loop. This distinction is important because a Generator need not return the same result each time it is invoked; it is permitted to read from a file, refer to and modify local state, and so on.

[2] The reason that generate requires its argument to be a mutable Forward Iterator, rather than just an Output Iterator, is that it uses a range [first, last) of iterators. There is no sensible way to describe a range of Output Iterators, because it is impossible to compare two Output Iterators for equality. The generate_n algorithm does have an interface that permits use of an Output Iterator.