Defined in header <functional> | ||
---|---|---|
template< class Arg1, class Arg2, class Result > struct binary_function; | (until C++17) (deprecated since c++11) |
binary_function
is a base class for creating function objects with two arguments.
binary_function
does not define operator()
; it is expected that derived classes will define this. binary_function
provides only three types - first_argument_type
, second_argument_type
and result_type
- defined by the template parameters.
Some standard library function object adaptors, such as std::not2
, require the function objects they adapt to have certain types defined; std::not2
requires the function object being adapted to have two types named first_argument_type
and second_argument_type
. Deriving function objects that take two arguments from binary_function
is an easy way to make them compatible with those adaptors.
binary_function
is deprecated in C++11 and removed in C++17.
Member types
Type | Definition |
---|---|
first_argument_type | Arg1 |
second_argument_type | Arg2 |
result_type | Result |
Example
#include <algorithm> #include <functional> #include <iostream> #include <vector> struct same : std::binary_function<int, int, bool> { bool operator()(int a, int b) const { return a == b; } }; int main() { std::vector<int> v1{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}; std::vector<int> v2{10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 }; std::vector<bool> v3(v1.size()); std::transform(v1.begin(), v1.end(), v2.begin(), v3.begin(), std::not2(same())); std::cout << std::boolalpha; for (std::size_t i = 0; i < v1.size(); ++i) std::cout << v1[i] << ' ' << v2[i] << ' ' << v3[i] << '\n'; }
Output:
0 10 true 1 9 true 2 8 true 3 7 true 4 6 true 5 5 false 6 4 true 7 3 true 8 2 true 9 1 true 10 0 true
See also
(C++11) | wraps callable object of any type with specified function call signature (class template) |
(until C++17) | creates an adaptor-compatible function object wrapper from a pointer to function (function template) |
(until C++17) | adaptor-compatible wrapper for a pointer to binary function (class template) |
(until C++17) | adaptor-compatible unary function base class (class template) |
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