std::operators (match_results)

equality (1)	template <class BidirectionalIterator, class Alloc> bool operator== ( const match_results<BidirectionalIterator,Alloc>& lhs, const match_results<BidirectionalIterator,Alloc>& rhs );
inequality (2)	template <class BidirectionalIterator, class Alloc> bool operator!= ( const match_results<BidirectionalIterator,Alloc>& lhs, const match_results<BidirectionalIterator,Alloc>& rhs );

equality (1)

template <class BidirectionalIterator, class Alloc>
  bool operator== ( const match_results<BidirectionalIterator,Alloc>& lhs,
                    const match_results<BidirectionalIterator,Alloc>& rhs );

inequality (2)

template <class BidirectionalIterator, class Alloc>
  bool operator!= ( const match_results<BidirectionalIterator,Alloc>& lhs,
                    const match_results<BidirectionalIterator,Alloc>& rhs );

Relational operators for match_results

Returns the result of the appropriate equality or inequality comparison operation between the match_results objects lhs and rhs.

The procedure for the equality comparison is as follows (stopping at any point if the procedure finds a conclusive answer):

If neither object is ready, true.
If only one object is ready, false.
If both objects are empty, true.
If both prefixes do not compare equal, false.
If both sizes are different, false.
If the algorithm equal would return false for comparing the ranges of sub_match elements in both objects, false.
If both suffixes are equal, true.
Otherwise, false.

For the inequality comparison, the result is the opposed one.

Parameters

lhs, rhs: match_results containers (to the left- and right-hand side of the operator, respectively), having both the same template parameters (BidirectionalIterator and Alloc).

Return Value

true if the condition holds, and false otherwise.

Example

// match_results comparisons
// - using cmatch, a standard alias of match_results<const char*>
#include <iostream>
#include <regex>

int main ()
{
  std::cmatch m1,m2,m3;

  std::regex_search ( "a needle in the haystack", m1, std::regex("needle") );
  std::regex_search ( "a needle in the haystack", m2, std::regex("needle") );
  std::regex_search ( "the needle in a haystack", m3, std::regex("needle") );

  if (m1==m2) std::cout << "m1 and m2 are equal\n";
  if (m2!=m3) std::cout << "m2 and m3 are not equal\n";  // prefix() don't match

  return 0;
}