collate::do_compare

virtual int do_compare(const E *first1, const E *last1,
    const E *first2, const E *last2) const;

The protected virtual member function compares the sequence at [first1, last1) with the sequence at [first2, last2). It compares values by applying operator< between pairs of corresponding elements of type E. The first sequence compares less if it has the smaller element in the earliest unequal pair in the sequences, or if no unequal pairs exist but the first sequence is shorter.

If the first sequence compares less than the second sequence, the function returns -1. If the second sequence compares less, the function returns +1. Otherwise, the function returns zero.