find_if()

Module:  Standard C++ Library   Library:  Algorithms

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Algorithm that finds an occurrence of a value in a sequence that satisfies a specified predicate

#include <algorithm>

namespace std {
  template <class InputIterator, class Predicate>
  InputIterator find_if(InputIterator start,
                        InputIterator finish,
                        Predicate pred);
}

The find_if() algorithm allows you to search for the first element in a sequence that satisfies a particular condition. The sequence is defined by iterators start and finish, while the condition is defined by the third argument: a predicate function that returns a boolean value. find_if() returns the first iterator i in the range [start, finish) for which the following condition holds:

pred(*i) == true.

If no such iterator is found, find_if() returns finish.

find_if() performs at most finish-start applications of the corresponding predicate.

//
//  find.cpp
//

#include <vector>      // for vector
#include <algorithm>   // for adjacent_find, find
#include <functional>  // for bind1st, equal_to
#include <iostream>    // for cout, endl



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

    const Vector::value_type arr[] = { 0, 1, 2, 2, 3, 
                                       4, 2, 2, 6, 7 };

    // Set up a vector.
    const Vector v1 (arr, arr + sizeof arr / sizeof *arr);

    // Try find.
    Vector::const_iterator it = std::find (v1.begin (), 
                                           v1.end (), 3);

    std::cout << *it << ' ';

    // Try find_if.
    it = std::find_if (v1.begin (), v1.end (),
             std::bind1st (std::equal_to<Vector::value_type>(), 
             3));

    std::cout << *it << ' ';

    // Try both adjacent_find variants.
    it = std::adjacent_find (v1.begin (), v1.end ());

    std::cout << *it << ' ';

    it = std::adjacent_find (v1.begin (), v1.end (),
                          std::equal_to<Vector::value_type>());

    std::cout << *it << std::endl;

    return 0;
}


Program Output:

3 3 2 2

adjacent_find(), Algorithms, find(), find_end(), find_first_of()

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.1.2

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Licensed under the Apache License, Version 2.0.
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