Man Page lexicographical_compare.3

                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.

NAME

     lexicographical_compare

      - Compares two ranges lexicographically.

SYNOPSIS

     #include <algorithm>
     template <class InputIterator1, class InputIterator2>
     bool
      lexicographical_compare(InputIterator1 first,
                             InputIterator2 last1,
                             InputIterator2 first2,
                             InputIterator last2);

     template <class InputIterator1, class InputIterator2,
              class Compare>
     bool
      lexicographical_compare(InputIterator1 first,
                             InputIterator2 last1,
                             InputIterator2 first2,
                             InputIterator last2, Compare comp);

DESCRIPTION

     The lexicographical_compare functions compare  each  element
     in the range [first1, last1) to the corresponding element in
     the range [first2, last2) using iterators i and j.

     The first version of the algorithm  uses  operator<  as  the
     default  comparison operator. It immediately returns true if
     it encounters any pair in which *i  is  less  than  *j,  and
     immediately  returns  false  if  *j  is less than *i. If the
     algorithm reaches the  end  of  the  first  sequence  before
     reaching  the  end  of  the second sequence, it also returns
     true.

     The second version of the function takes  an  argument  comp
     that  defines a comparison function that is used in place of
     the default operator<.

     The lexicographical_compare functions can be used  with  all
     the datatypes included in the standard library.

COMPLEXITY

     lexicographical_compare  performs  at  most   min((last1   -
     first1),  (last2  -  first2)) applications of the comparison
     function.

EXAMPLE

     //
     // lex_comp.cpp
     //
      #include <algorithm>
      #include <vector>
      #include <functional>
      #include <iostream>
     using namespace std;

     int main(void)
      {
       int d1[5] = {1,3,5,32,64};
       int d2[5] = {1,3,2,43,56};

        // set up vector
       vector<int> v1(d1,d1 + 5), v2(d2,d2 + 5);

        // Is v1 less than v2 (I think not)
       bool b1 = lexicographical_compare(v1.begin(),
                  v1.end(), v2.begin(), v2.end());

        // Is v2 less than v1 (yup, sure is)
       bool b2 = lexicographical_compare(v2.begin(),
                v2.end(), v1.begin(), v1.end(), less<int>());
       cout << (b1 ? "TRUE" : "FALSE") << " "
             << (b2 ? "TRUE" : "FALSE") << endl;

       return 0;
      }

     Program Output




     FALSE TRUE

WARNINGS

     If your compiler does not support default  template  parame-
     ters,  then you always need to supply the Allocator template
     argument. For instance, you have to write:

     vector<int, allocator<int> >

     instead of:

     vector<int>

     If your compiler does not support namespaces,  then  you  do
     not need the using declaration for std.