std::generate_n

 

C++

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all_of any_of none_of (C++11) (C++11) (C++11) for_each count count_if mismatch equal	find find_if find_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copy copy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n remove remove_if remove_copy remove_copy_if	replace replace_if replace_copy replace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffle shuffle   (C++11) unique unique_copy
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C library
qsort	bsearch

 

Defined in header <algorithm>
template< class OutputIterator, class Size, class Generator > void generate_n( OutputIterator first, Size count, Generator g ); template< class OutputIterator, class Size, class Generator > OutputIterator generate_n( OutputIterator first, Size count, Generator g );		(until C++11) (since C++11)

Assigns values, generated by given function object g, to the first count elements in the range beginning at first, if count>0. Does nothing otherwise.

Parameters

first	-	the beginning of the range of elements to generate
count	-	number of the 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 OutputIterator can be dereferenced and assigned a value of type  Ret. ​

Return value

(none) (until C++11)

Iterator one past the last element assigned if count>0, first otherwise. (since C++11)

Complexity

Exactly count invocations of g() and assignments, for count>0.

Possible implementation

template< class OutputIterator, class Size, class Generator > OutputIterator generate_n( OutputIterator first, Size count, Generator g ) { for( Size i = 0; i < count; i++ ) { *first++ = g(); } return first; }

Example

The following code fills an array of integers with random numbers.

#include <cstddef>
#include <cstdlib>
#include <iostream>
#include <iterator>
#include <algorithm>
 
int main()
{
    const std::size_t N = 5;
    int ar[N];
    std::generate_n(ar, N, std::rand); // Using the C function rand()
 
    std::cout << "ar: ";
    std::copy(ar, ar+N, std::ostream_iterator<int>(std::cout, " "));
    std::cout << "\n";
}

Output:

52894 15984720 41513563 41346135 51451456

See also

fill_n	assigns a value to a number of elements (function template)
generate	saves the result of a function in a range (function template)