map查找value

#include <iostream>
#include <algorithm>
#include <map>
using namespace std;

/* function object to check the value of a map element */
template <class K, class V>
class value_equals 
{
  private:
    V value;
  public:
    // constructor (initialize value to compare with)
    value_equals (const V& v) : value(v) {}
    // comparison
    bool operator() (pair<const K, V> elem) 
    {
        return elem.second == value;
    }
};

int main()
{
    typedef map<float,float> FloatFloatMap;
    FloatFloatMap coll;
    FloatFloatMap::iterator pos;

    // fill container
    coll[1]=7;
    coll[2]=4;
    coll[3]=2;
    coll[4]=3;
    coll[5]=6;
    coll[6]=1;
    coll[7]=3;

    // search an element with value 3.0
    pos = find_if(coll.begin(),coll.end(), value_equals<float,float>(3.0));
    if (pos != coll.end()) 
    {
        cout << pos->first << ": " << pos->second << endl;
    }
}