Pair Logical Operator

Veranschaulicht, wie die Funktion der Standardvorlagenbibliothek (STL) Paare logischen Operators in Visual C++ verwendet.

Hinweis
Nur operator< und operator== sind erforderlich, um alle logischen Operatoren zu definieren.

template<class _T1, class _T2> inline
   bool operator==(
      const pair<_T1, _T2>& _X,
      const pair<_T1, _T2>& _Y
   ) {return ( _X.first == _Y.first && _X.second == _Y.second ); }
template<class _T1, class _T2> inline
   bool operator<(
      const pair<_T1, _T2>& _X,
      const pair<_T1, _T2>& _Y
   ) {return ( 
        _X.first < _Y.first || !( _Y.first < _X.first) 
        && _X.second < _Y.second
   ); }

Hinweise

Hinweis
Die Klasse/Parameternamen im Prototyp stimmen nicht mit der Version in der Headerdatei ab.Einige wurden geändert, um die Lesbarkeit zu verbessern.

Die Funktionen werden im Kommentarteil des Beispiels beschrieben.

Beispiel

// paircomp.cpp
// compile with: /EHsc
// Illustrates several comparison operators used to compare two
// pair objects.
//
// Functions:
//    operator== - returns true if two pair objects are identical.
//
//    operator!= - returns true if two pair objects are not identical.
//
//    operator<  - returns true for (A < B) if pair object A is less
//                 than pair object B.
//
//    operator<= - returns true for (A <= B) if pair object A is less
//                 than or equal to pair object B.
//
//    operator>  - returns true for (A > B) if pair object A is greater
//                 than pair object B.
//
//    operator>= - returns true for (A >= B) if pair object A is greater
//                 than or equal to pair object B.
/////////////////////////////

#include <iostream>
#include <utility>

using namespace std ;

/* STL pair data type containing int and float */

typedef struct pair<int, float> PAIR_IF;

int main(void)
{
  PAIR_IF A(10,3.14f);
  PAIR_IF B(18,3.14f);
  PAIR_IF C(10,6.28f);
  PAIR_IF D(10,3.14f);

/* show pair values */

  cout << "A = ( " << A.first << " , " << A.second << " )" << endl;
  cout << "B = ( " << B.first << " , " << B.second << " )" << endl;
  cout << "C = ( " << C.first << " , " << C.second << " )" << endl;
  cout << "D = ( " << D.first << " , " << D.second << " )" << endl;

/* operator== */

  if (A==D)
    cout << "A and D are equal" << endl;
  else
    cout << "A and D are not equal" << endl;

/* operator!= */

  if (B!=C)
    cout << "B and C are not equivalent" << endl;
  else
    cout << "B and C are equivalent" << endl;

/* operator> */

  if (A>C)
    cout << "A is greater than C" << endl;
  else
    cout << "A is not greater than C" << endl;

/* operator>= */

  if (A>=C)
    cout << "A is greater than or equal to C" << endl;
  else
    cout << "A is not greater than or equal to C" << endl;

/* operator< */

  if (C<D)
    cout << "C is less than D" << endl;
  else
    cout << "C is not less than D" << endl;

/* operator<= */

  if (C<D)
    cout << "C is less than or equal to D" << endl;
  else
    cout << "C is not less than or equal to D" << endl;
}

Output

A = ( 10 , 3.14 )
B = ( 18 , 3.14 )
C = ( 10 , 6.28 )
D = ( 10 , 3.14 )
A and D are equal
B and C are not equivalent
A is not greater than C
A is not greater than or equal to C
C is not less than D
C is not less than or equal to D

Anforderungen

Header: <utility>

Siehe auch

Konzepte

Standardvorlagenbibliotheks-Beispiele