operator< (<utility>)

Artikel
07/29/2015

Tests if the pair object on the left side of the operator is less than the pair object on the right side.

template<class Type1, class Type2> 
   bool operator<( 
      const pair<Type1, Type2>& _Left, 
      const pair<Type1, Type2>& _Right 
   );

Parameters

_Left
An object of type pair on the left side of the operator.
_Right
An object of type pair on the right side of the operator.

Return Value

true if the pair on the left side of the operator is strictly less than the pair on the right side of the operator; otherwise false.

Remarks

The _Left pair object is said to be strictly less than the _Right pair object if _Left is less than and not equal _Right.

In a comparison of pairs, the values' first elements of the two pairs have the highest priority. If they differ, then the result of their comparison is taken as the result of the comparison of the pair. If the values of the first elements are not different, then the values of the second elements are compared and the result of their comparison is taken as the result of the comparison of the pair.

Example

// utility_op_lt.cpp
// compile with: /EHsc
#include <utility>
#include <iomanip>
#include <iostream>

int main( )
{
   using namespace std;
   pair <int, double> p1, p2, p3;

   p1 = make_pair ( 10, 2.22e-1 );
   p2 = make_pair ( 100, 1.11e-1 );
   p3 = make_pair ( 10, 1.11e-1 );

   cout.precision ( 3 );
   cout << "The pair p1 is: ( " << p1.first << ", " 
        << p1.second << " )." << endl;
   cout << "The pair p2 is: ( " << p2.first << ", " 
        << p2.second << " )." << endl;
   cout << "The pair p3 is: ( " << p3.first << ", " 
        << p3.second << " )." << endl << endl;

   if ( p1 < p2 )
      cout << "The pair p1 is less than the pair p2." << endl;
   else
      cout << "The pair p1 is not less than the pair p2." << endl;

   if ( p1 < p3 )
      cout << "The pair p1 is less than the pair p3." << endl;
   else
      cout << "The pair p1 is not less than the pair p3." << endl;
}

The pair p1 is: ( 10, 0.222 ).
The pair p2 is: ( 100, 0.111 ).
The pair p3 is: ( 10, 0.111 ).

The pair p1 is less than the pair p2.
The pair p1 is not less than the pair p3.

Requirements

Header: <utility>

Namespace: std

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