Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://cplusplus.com/function::target below:

public member function

<functional>

template <class TargetType>       TargetType* target() noexcept;template <class TargetType> const TargetType* target() const noexcept;

Get pointer to target

Because function is a polymorphic wrapper class, it is unaware of the static type of its target callable object, and thus the template parameter TargetType must be explicitly specified.

TargetType shall match the target type, so that typeid(TargetType)==target_type(). Otherwise, the function always returns a null pointer.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25

// function::target example
#include <iostream>     // std::cout, std::boolalpha
#include <functional>   // std::function, std::plus, std::minus

int my_plus (int a, int b) {return a+b;}
int my_minus (int a, int b) {return a-b;}

int main () {
  std::function<int(int,int)> foo = my_plus;
  std::function<int(int,int)> bar = std::plus<int>();

  // calling using functional form:
  std::cout << foo(100,20) << '\n';
  std::cout << bar(100,20) << '\n';

  // calling by invoking target:
  std::cout << (*foo.target<int(*)(int,int)>())(100,20) << '\n';
  std::cout << (*bar.target<std::plus<int>>())(100,20) << '\n';

  // changing target directly:
  *foo.target<int(*)(int,int)>() = &my_minus;
  std::cout << foo(100,20) << '\n';

  return 0;
}

function::operator()

Call target (public member function)

function::target_type

Target type_info (public member function)

RetroSearch is an open source project built by @garambo | Open a GitHub Issue

Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo

HTML: 3.2 | Encoding: UTF-8 | Version: 0.7.4