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count(3C++)			       -			   count(3C++)

Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.

NAME
       count, count_if

	-  Count  the  number  of elements in a container that satisfy a given
       condition.

SYNOPSIS
       #include <algorithm>
       template<class InputIterator, class T>
       typename iterator_traits<InputIterator>::difference_type
       count(InputIterator first, InputIterator last,
      const T& value);
template <;class InputIterator, class T, class Size>
void count(InputIterator first, InputIterator last,
	   const T& value, Size& n);
template<;class InputIterator, class Predicate>
typename iterator_traits<;InputIterator>::difference_type
count_if(InputIterator first, InputIterator last,
	 Predicate pred);
template <;class InputIterator, class Predicate, class Size>
void count_if(InputIterator first, InputIterator last,
	      Predicate pred, Size& n);

DESCRIPTION
       The count algorithm compares value to elements in the sequence  defined
       by  iterators  first  and  last. The first version of count returns the
       number of matches. The second version increments	 a  counting  value  n
       each  time  it finds a match. In other words, count returns (or adds to
       n) the number of iterators i in the range [first, last) for  which  the
       following condition holds:

       *i == value

       Type T must be EqualityComparable.

COMPLEXITY
       The  count_if  algorithm	 lets you specify a predicate, and returns the
       number of times an element in the sequence satisfies the predicate  (or
       increments  n that number of times). That is, count_if returns (or adds
       to n) the number of iterators i in the range [first,  last)  for	 which
       the following condition holds:

       pred(*i) == true.

       Both  count and count_if perform exactly last-first applications of the
       corresponding predicate.

EXAMPLE
//
// count.cpp
//
// Does not demonstrate the partial specialization versions
// of count and count_if
//
 #include <vector>
 #include <algorithm>
 #include <iostream>
using namespace std;

int main()
 {
  int sequence[10] = {1,2,3,4,5,5,7,8,9,10};
  int i=0,j=0,k=0;
   //
   // Set up a vector
   //
  vector<int> v(sequence,sequence + 10);

  count(v.begin(),v.end(),5,i);	 // Count fives
  count(v.begin(),v.end(),6,j);	 // Count sixes
   //
   // Count all less than 8
   // I=2, j=0
   //
  count_if(v.begin(),v.end(),bind2nd(less<int>(),8),k);
   // k = 7

  cout << i << " " << j << " " << k << endl;
  return 0;
 }

Program Output

2 0 7

WARNINGS
       If your compiler does not  support  partial  specialization,  then  the
       first  version  of  both	 count	and count_if (the one that returns the
       count) is not available.

       If your compiler does not support default template parameters, then you
       always  need  to	 supply the Allocator template argument. For instance,
       you have to write:

       vector <int, allocator<int> >

       instead of:

       vector <int>

       If your compiler does not support namespaces, then you do not need  the
       using declaration for std.

Rogue Wave Software		  02 Apr 1998			   count(3C++)
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