fill(), fill_n()

Library:  Algorithms

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Algorithm that assigns the same value to the elements in a given range

#include <algorithm>

namespace std {
  template <class ForwardIterator, class T>
   void fill(ForwardIterator start, ForwardIterator finish,
             const T& value);

  template <class OutputIterator, class Size, class T>
  void fill_n(OutputIterator start, Size n, const T& value);
}

The fill() and fill_n() algorithms are used to assign a value to the elements in a sequence. fill() assigns the value to all the elements designated by iterators in the range [start, finish).

The fill_n() algorithm assigns the value to all the elements designated by iterators in the range [start, start + n). fill_n() assumes that all iterators in the range [start, start + n) are dereferenceable, unless start is an insert iterator.

Type T must be Assignable, and Size must be convertible to an integral type.

fill() makes exactly finish - start assignments, and fill_n() makes exactly n assignments.

//
// fill.cpp
//

#include <algorithm>
#include <iostream>
#include <vector>  



int main ()
{
    // Typedef for convenience.
    typedef std::vector<int, std::allocator<int> > vector;

    const vector::value_type arr[] = { 1, 2, 3, 4 };

    // Set up two vectors.
    vector v1(arr, arr + sizeof arr / sizeof *arr);
    vector v2(v1.begin (), v1.end ());

    // Set up one empty vector.
    vector v3;

    // Fill all of v1 with 9.
    std::fill(v1.begin (), v1.end (), 9);

    // Fill first 3 of v2 with 7.
    std::fill_n(v2.begin (), 3, 7);

    // Use insert iterator to fill v3 with 5 11's.
    std::fill_n(std::back_inserter (v3), 5, 11);

    // Copy all three to cout.
    std::ostream_iterator<vector::value_type, char,
             std::char_traits<char> > out(std::cout, " ");

    std::copy(v1.begin (), v1.end (), out);
    std::cout << std::endl;

    std::copy(v2.begin (), v2.end (), out);
    std::cout << std::endl;

    std::copy(v3.begin (), v3.end (), out);
    std::cout << std::endl;

    // Fill cout with 3 5's.
    std::fill_n(out, 3, 5);
    std::cout << std::endl;

    return 0;
}


Program Output

9 9 9 9 
7 7 7 4 
11 11 11 11 11 
5 5 5 

Algorithms

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.2.5