# 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> >

vector<int>

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

```