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std::generate

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< cpp‎ | algorithm
Revision as of 15:53, 17 October 2013 by Nate (Talk | contribs)

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Defined in header <algorithm>
template< class ForwardIt, class Generator >
void generate( ForwardIt first, ForwardIt last, Generator g );

Assigns each element in range [first, last) a value generated by the given function object g.

Contents

[edit] Parameters

first, last - the range of elements to generate
g - generator function object that will be called.

The signature of the function should be equivalent to the following:

Ret fun();

The type Ret must be such that an object of type ForwardIt can be dereferenced and assigned a value of type Ret. ​

Type requirements
-
ForwardIt must meet the requirements of ForwardIterator.

[edit] Return value

(none)

[edit] Complexity

Exactly std::distance(first, last) invocations of g() and assignments.

[edit] Possible implementation

template<class ForwardIt, class Generator>
void generate(ForwardIt first, ForwardIt last, Generator g)
{
    while (first != last) {
        *first++ = g();
    }
}

[edit] Example

The following code fills a vector with random numbers:

#include <algorithm>
#include <iostream>
#include <cstdlib>
 
int main()
{
    std::vector<int> v(5);
    std::generate(v.begin(), v.end(), std::rand); // Using the C function rand()
 
    std::cout << "v: ";
    for (auto iv: v) {
        std::cout << iv << " ";
    }
    std::cout << "\n";
 
    // Initialize with default values 0,1,2,3,4 from a lambda function
    int n(0);
    std::generate(v.begin(), v.end(), [&]{ return n++; }); 
 
    std::cout << "v: ";
    for (auto iv: v) {
        std::cout << iv << " ";
    }
    std::cout << "\n";
}

Possible output:

v: 52894 15984720 41513563 41346135 51451456
v: 0 1 2 3 4

[edit] See also

assigns a range of elements a certain value
(function template) [edit]
saves the result of N applications of a function
(function template) [edit]