std::map find_if condition style confusion

Question

I\'d like to use std::find_if to search for the first element in my map that has a certain value in a specific element of its value structure. I\'m a little confus

Answer 1

Elements in the map are not sorted by value, they are sorted according to the key. So the phrase "the first element" has not much sense.

To find some element (not the first) that has x equal to some value you can write the functor as follows:

struct check_x
{
  check_x( int x ) : x_(x) {}
  bool operator()( const std::pair& v ) const 
  { 
    return v.second.x == x_; 
  }
private:
  int x_;
};

Then use it as follows:

// find any element where x equal to 10
std::find_if( myMap.begin(), myMap.end(), check_x(10) );