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# lexicographical_compare

Visual Studio 2008

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.

Namespace: std