less

     Function Object

Binary function object that returns true if its first argument is less than its second

Contents

• Synopsis
• Description
• Interface
• Warning
• See Also

#include<functional>

template <class T>
struct less : public binary_function<T, T, bool> ;

less is a binary function object. Its operator() returns true if x is less than y. You can pass a less object to any algorithm that requires a binary function. For example, the transform algorithm applies a binary operation to corresponding values in two collections and stores the result of the function. less would be used in that algorithm in the following manner:

vector<int> vec1;

vector<int> vec2;
vector<int> vecResult;
.
.
.
transform(vec1.begin(), vec1.end(),          vec2.begin(),
          vecResult.begin(), less<int>());

After this call to transform, vecResult(n) will contain a "1" if vec1(n) was less than vec2(n) or a "0" if vec1(n) was greater than or equal to vec2(n).

template <class T>

struct less : binary_function<T, T, bool> {
  typedef typename binary_function<T, T, bool>::second_argument_type 
                                                second_argument_type;
  typedef typename binary_function<T, T, bool>::first_argument_type 
                                                first_argument_type;
  typedef typename binary_function<T, T, bool>::result_type 
                                                result_type;
  bool operator() (const T&, const T&) const;
};

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

vector<int, allocator>

instead of

vector<int>

binary_function, Function Objects