less

Function Object

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A binary function object that returns true if its first argument is less than its second.

None

#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) contains 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> {
  bool operator() (const T&, const T&) const;
};

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

vector<int, allocator<int> >

instead of

vector<int>

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

binary_function, Function Objects