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如何使用BoostBinaryFunction概念?

template-meta-programming metaprogramming boost c++

0

Dr.Knowitall · 技术社区 · 7 年前

我找不到任何文档,也找不到任何与谷歌搜索相关的文档:

我有一个函数,我想生成一个签名:

(void)(int,int)

所以当我运行这两个函数时:

void dosomething(int x, int y);
void dosomethingwront(float x, float y);

通过:

// Should succeed
boost::BinaryFunction<dosomething,void,int,int>
// Should fail
boost::BinaryFunction<dosomethingwrong,void,int,int>

编译失败,因为它不喜欢第一个参数类型。不幸的是,我不知道他们的意思是什么 <class Func,...> 在他们的文件中。如果我有这两个函数,如何测试这些概念?

谢谢

1 回复 | 直到 7 年前

1

Henri Menke 7 年前

decltype((dosomething)) dosomethingwront int float

#include <boost/concept_check.hpp>

void dosomething(int x, int y);
void dosomethingwront(float x, float y);

int main() {
    BOOST_CONCEPT_ASSERT((boost::BinaryFunction<decltype((dosomething)),void,int,int>));
    BOOST_CONCEPT_ASSERT((boost::BinaryFunction<decltype((dosomethingwront)),void,int,int>));
}

#include <iostream>
#include <type_traits>

template <typename F>
struct is_void_int_int : std::false_type {};

// Free function
template <>
struct is_void_int_int<void(int, int)> : std::true_type {};

// Pointer to function
template <>
struct is_void_int_int<void (*)(int, int)> : std::true_type {};

// Reference to function
template <>
struct is_void_int_int<void (&)(int, int)> : std::true_type {};

// Pointer to member function
template <typename C>
struct is_void_int_int<void (C::*)(int, int)> : std::true_type {};

void dosomething(int x, int y);
void dosomethingwront(float x, float y);

struct A {
    void operator()(int, int) {}
};

struct B {
    void bar(int, int) {}
};

int main() {
    static_assert(is_void_int_int<decltype(dosomething)>::value, "!");
    static_assert(is_void_int_int<decltype((dosomething))>::value, "!");
    static_assert(is_void_int_int<decltype(&dosomething)>::value, "!");
    static_assert(is_void_int_int<decltype(&A::operator())>::value, "!");
    static_assert(is_void_int_int<decltype(&B::bar)>::value, "!");
  //static_assert(is_void_int_int<decltype(dosomethingwront)>::value, "!"); // BOOM!
}