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          The header file 'equal.hpp' contains two variants of a the stl algorithm
          equal. The algorithm tests
          to see if two sequences contain equal values;
        
          Before (the proposed) C++14 the algorithm std::equal
          took three iterators and an optional comparison predicate. The first two
          iterators [first1, last1) defined a sequence, and the second one
          first2 defined the start
          of the second sequence. The second sequence was assumed to be the same
          length as the first.
        
          In C++14, two new variants were introduced, taking four iterators and an
          optional comparison predicate. The four iterators define two sequences
          [first1, last1) and [first2, last2)
          explicitly, rather than defining the second one implicitly. This leads
          to correct answers in more cases (and avoid undefined behavior in others).
        
Consider the two sequences:
auto seq1 = { 0, 1, 2 }; auto seq2 = { 0, 1, 2, 3, 4 }; std::equal ( seq1.begin (), seq1.end (), seq2.begin ()); // true std::equal ( seq2.begin (), seq2.end (), seq1.begin ()); // Undefined behavior std::equal ( seq1.begin (), seq1.end (), seq2.begin (), seq2.end ()); // false
          You can argue that true is
          the correct answer in the first case, even though the sequences are not
          the same. The first N entries in seq2
          are the same as the entries in seq1
          - but that's not all that's in seq2.
          But in the second case, the algorithm will read past the end of seq1, resulting in undefined behavior
          (large earthquake, incorrect results, pregnant cat, etc).
        
However, if the two sequences are specified completely, it's clear that they are not equal.
          The function equal returns
          true if the two sequences compare equal; i.e, if each element in the sequence
          compares equal to the corresponding element in the other sequence. One
          version uses std::equal_to to do the comparison; the other
          lets the caller pass predicate to do the comparisons.
        
template <class InputIterator1, class InputIterator2> bool equal ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2 ); template <class InputIterator1, class InputIterator2, class BinaryPredicate> bool equal ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, BinaryPredicate pred );
          Given the container c1
          containing { 0, 1,
          2, 3, 14, 15 },
          and c2 containing { 1,
          2, 3 }, then
equal ( c1.begin (), c1.end (), c2.begin (), c2.end ()) --> false equal ( c1.begin () + 1, c1.begin () + 3, c2.begin (), c2.end ()) --> true equal ( c1.end (), c1.end (), c2.end (), c2.end ()) --> true // empty sequences are alway equal to each other
          equal works on all iterators
          except output iterators.
        
          Both of the variants of equal
          run in O(N) (linear) time; that is, they compare against
          each element in the list once. If the sequence is found to be not equal
          at any point, the routine will terminate immediately, without examining
          the rest of the elements.
        
          Both of the variants of equal
          take their parameters by value and do not depend upon any global state.
          Therefore, all the routines in this file provide the strong exception guarantee.
        
equal
              is part of the C++14 standard. When C++14 standard library implementations
              become available, the implementation from the standard library should
              be used.
            equal returns true
              for two empty ranges, no matter what predicate is passed to test against.
            
          The header file 'mismatch.hpp' contains two variants of a the stl algorithm
          mismatch. The algorithm
          finds the first point in two sequences where they do not match.
        
          Before (the proposed) C++14 the algorithm std::mismatch
          took three iterators and an optional comparison predicate. The first two
          iterators [first1, last1) defined a sequence, and the second one
          first2 defined the start
          of the second sequence. The second sequence was assumed to be the same
          length as the first.
        
          In C++14, two new variants were introduced, taking four iterators and an
          optional comparison predicate. The four iterators define two sequences
          [first1, last1) and [first2, last2)
          explicitly, rather than defining the second one implicitly. This leads
          to correct answers in more cases (and avoid undefined behavior in others).
        
Consider the two sequences:
auto seq1 = { 0, 1, 2 }; auto seq2 = { 0, 1, 2, 3, 4 }; std::mismatch ( seq1.begin (), seq1.end (), seq2.begin ()); // <3, 3> std::mismatch ( seq2.begin (), seq2.end (), seq1.begin ()); // Undefined behavior std::mismatch ( seq1.begin (), seq1.end (), seq2.begin (), seq2.end ()); // <3, 3>
          The first N entries in seq2
          are the same as the entries in seq1
          - but that's not all that's in seq2.
          In the second case, the algorithm will read past the end of seq1, resulting in undefined behavior
          (large earthquake, incorrect results, pregnant cat, etc).
        
However, if the two sequences are specified completely, it's clear that where the mismatch occurs.
          The function mismatch returns
          a pair of iterators which denote the first mismatching elements in each
          sequence. If the sequences match completely, mismatch
          returns their end iterators. One version uses std::equal_to
          to do the comparison; the other lets the caller pass predicate to do the
          comparisons.
        
template <class InputIterator1, class InputIterator2> std::pair<InputIterator1, InputIterator2> mismatch ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2 ); template <class InputIterator1, class InputIterator2, class BinaryPredicate> std::pair<InputIterator1, InputIterator2> mismatch ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, BinaryPredicate pred );
          Given the container c1
          containing { 0, 1,
          2, 3, 14, 15 },
          and c2 containing { 1,
          2, 3 }, then
mismatch ( c1.begin(), c1.end(), c2.begin(), c2.end()) --> <c1.begin(), c2.begin()> // first elements do not match mismatch ( c1.begin() + 1, c1.begin() + 4, c2.begin(), c2.end()) --> <c1.begin() + 4, c2.end ()> // all elements of `c2` match mismatch ( c1.end(), c1.end(), c2.end(), c2.end()) --> <c1.end(), c2.end()> // empty sequences don't match at the end.
          mismatch works on all iterators
          except output iterators.
        
          Both of the variants of mismatch
          run in O(N) (linear) time; that is, they compare against
          each element in the list once. If the sequence is found to be not equal
          at any point, the routine will terminate immediately, without examining
          the rest of the elements.
        
          Both of the variants of mismatch
          take their parameters by value and do not depend upon any global state.
          Therefore, all the routines in this file provide the strong exception guarantee.
        
mismatch
              is part of the C++14 standard. When C++14 standard library implementations
              become available, the implementation from the standard library should
              be used.