# lexicographical_compare

Compares element by element between two sequences to determine which is lesser of the two.

```
template<class InputIterator1, class InputIterator2>
bool lexicographical_compare(
InputIterator1 _First1,
InputIterator1 _Last1,
InputIterator2 _First2,
InputIterator2 _Last2
);
template<class InputIterator1, class InputIterator2, class BinaryPredicate>
bool lexicographical_compare(
InputIterator1 _First1,
InputIterator1 _Last1,
InputIterator2 _First2,
InputIterator2 _Last2,
BinaryPredicate _Comp
);
```

## Parameters

_First1

An input iterator addressing the position of the first element in the first range to be compared._Last1

An input iterator addressing the position one past the final element in the first range to be compared._First2

An input iterator addressing the position of the first element in the second range to be compared._Last2

An input iterator addressing the position one past the final element in the second range to be compared._Comp

User-defined predicate function object that defines sense in which one element is less than another. A binary predicate takes two arguments and returns**true**when satisfied and**false**when not satisfied.

## Return Value

**true** if the first range is lexicographically less than the second range; otherwise **false**.

## Remarks

A lexicographical comparison between sequences compares them element by element until:

It finds two corresponding elements unequal, and the result of their comparison is taken as the result of the comparison between sequences.

No inequalities are found, but one sequence has more elements than the other, and the shorter sequence is considered less than the longer sequence.

No inequalities are found and the sequences have the same number of elements, and so the sequences are equal and the result of the comparison is false.

## Example

```
// alg_lex_comp.cpp
// compile with: /EHsc
#include <vector>
#include <list>
#include <algorithm>
#include <iostream>
// Return whether second element is twice the first
bool twice ( int elem1, int elem2 )
{
return 2 * elem1 < elem2;
}
int main( )
{
using namespace std;
vector <int> v1, v2;
list <int> L1;
vector <int>::iterator Iter1, Iter2;
list <int>::iterator L1_Iter, L1_inIter;
int i;
for ( i = 0 ; i <= 5 ; i++ )
{
v1.push_back( 5 * i );
}
int ii;
for ( ii = 0 ; ii <= 6 ; ii++ )
{
L1.push_back( 5 * ii );
}
int iii;
for ( iii = 0 ; iii <= 5 ; iii++ )
{
v2.push_back( 10 * iii );
}
cout << "Vector v1 = ( " ;
for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )
cout << *Iter1 << " ";
cout << ")" << endl;
cout << "List L1 = ( " ;
for ( L1_Iter = L1.begin( ) ; L1_Iter!= L1.end( ) ; L1_Iter++ )
cout << *L1_Iter << " ";
cout << ")" << endl;
cout << "Vector v2 = ( " ;
for ( Iter2 = v2.begin( ) ; Iter2 != v2.end( ) ; Iter2++ )
cout << *Iter2 << " ";
cout << ")" << endl;
// Self lexicographical_comparison of v1 under identity
bool result1;
result1 = lexicographical_compare (v1.begin( ), v1.end( ),
v1.begin( ), v1.end( ) );
if ( result1 )
cout << "Vector v1 is lexicographically_less than v1." << endl;
else
cout << "Vector v1 is not lexicographically_less than v1." << endl;
// lexicographical_comparison of v1 and L2 under identity
bool result2;
result2 = lexicographical_compare (v1.begin( ), v1.end( ),
L1.begin( ), L1.end( ) );
if ( result2 )
cout << "Vector v1 is lexicographically_less than L1." << endl;
else
cout << "Vector v1 is lexicographically_less than L1." << endl;
bool result3;
result3 = lexicographical_compare (v1.begin( ), v1.end( ),
v2.begin( ), v2.end( ), twice );
if ( result3 )
cout << "Vector v1 is lexicographically_less than v2 "
<< "under twice." << endl;
else
cout << "Vector v1 is not lexicographically_less than v2 "
<< "under twice." << endl;
}
```

Vector v1 = ( 0 5 10 15 20 25 ) List L1 = ( 0 5 10 15 20 25 30 ) Vector v2 = ( 0 10 20 30 40 50 ) Vector v1 is not lexicographically_less than v1. Vector v1 is lexicographically_less than L1. Vector v1 is not lexicographically_less than v2 under twice.

## Requirements

**Header:** <algorithm>

**Namespace:** std