Книга: Standard Template Library Programmer

generate

generate

Category: algorithms

Component type: function

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

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

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

• 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]

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

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

[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.

copy, fill, fill_n, generate_n, iota

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