# less Struct

A binary predicate that performs the less-than operation (`operator<`

) on its arguments.

## Syntax

```
template <class Type = void>
struct less : public binary_function <Type, Type, bool>
{
bool operator()(const Type& Left, const Type& Right) const;
};
// specialized transparent functor for operator<
template <>
struct less<void>
{
template <class T, class U>
auto operator()(T&& Left, U&& Right) const
-> decltype(std::forward<T>(Left) <std::forward<U>(Right));
};
```

### Parameters

*Type*, *T*, *U*

Any type that supports an `operator<`

that takes operands of the specified or inferred types.

*Left*

The left operand of the less-than operation. The unspecialized template takes an lvalue reference argument of type *Type*. The specialized template does perfect forwarding of lvalue and rvalue reference arguments of inferred type *T*.

*Right*

The right operand of the less-than operation. The unspecialized template takes an lvalue reference argument of type *Type*. The specialized template does perfect forwarding of lvalue and rvalue reference arguments of inferred type *U*.

## Return Value

The result of `Left < Right`

. The specialized template does perfect forwarding of the result, which has the type that's returned by `operator<`

.

## Remarks

The binary predicate `less`

<`Type`

> provides a strict weak ordering of a set of element values of type *Type* into equivalence classes, if and only if this type satisfies the standard mathematical requirements for being so ordered. The specializations for any pointer type yield a total ordering of elements, in that all elements of distinct values are ordered with respect to each other.

## Example

```
// functional_less.cpp
// compile with: /EHsc
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>
struct MyStruct {
MyStruct(int i) : m_i(i){}
bool operator < (const MyStruct & rhs) const {
return m_i < rhs.m_i;
}
int m_i;
};
int main() {
using namespace std;
vector <MyStruct> v1;
vector <MyStruct>::iterator Iter1;
vector <MyStruct>::reverse_iterator rIter1;
int i;
for ( i = 0 ; i < 7 ; i++ )
v1.push_back( MyStruct(rand()));
cout << "Original vector v1 = ( " ;
for ( Iter1 = v1.begin() ; Iter1 != v1.end() ; Iter1++ )
cout << Iter1->m_i << " ";
cout << ")" << endl;
// To sort in ascending order,
sort( v1.begin( ), v1.end( ), less<MyStruct>());
cout << "Sorted vector v1 = ( " ;
for ( Iter1 = v1.begin() ; Iter1 != v1.end() ; Iter1++ )
cout << Iter1->m_i << " ";
cout << ")" << endl;
}
```

```
Original vector v1 = (41 18467 6334 26500 19169 15724 11478)
Sorted vector v1 = (41 6334 11478 15724 18467 19169 26500)
```

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