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8_1_3_functor-adapter.cpp
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97 lines (81 loc) · 2.69 KB
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// file: 8functor-adapter.cpp
#include <algorithm>
#include <functional>
#include <vector>
#include <iostream>
#include <iterator>
using namespace std;
// compose1在mingw中没有，所以把定义搬了过来
template <class _Operation1, class _Operation2>
class unary_compose
: public unary_function<typename _Operation2::argument_type,
typename _Operation1::result_type>
{
protected:
_Operation1 _M_fn1;
_Operation2 _M_fn2;
public:
unary_compose(const _Operation1& __x, const _Operation2& __y)
: _M_fn1(__x), _M_fn2(__y) {}
typename _Operation1::result_type
operator()(const typename _Operation2::argument_type& __x) const {
return _M_fn1(_M_fn2(__x));
}
};
template <class _Operation1, class _Operation2>
inline unary_compose<_Operation1,_Operation2>
compose1(const _Operation1& __fn1, const _Operation2& __fn2)
{
return unary_compose<_Operation1,_Operation2>(__fn1, __fn2);
}
void print(int i) {
cout << i << " ";
}
class Int {
public:
// explicit 只能修改只有一个参数的类构造函数，
// 或是除了第一个参数外其他参数都有默认值的情况
// 表明该构造函数是显示的而非隐式的
// 作用是禁止类构造函数的隐式自动转换
// implicit 表示隐式，类构造函数默认声明为隐式
// google c++规范与effective c++都推荐使用explicit声明
explicit Int(int i) : m_i(i) {}
void print1() const {
cout << "[" << m_i << "]";
}
private:
int m_i;
};
int main() {
// 将outite绑定到cout，每次对outite指派一个元素，就后接一个“ ”
ostream_iterator<int> outite(cout, " ");
int ia[6] = {2, 21, 12, 7, 19, 23};
vector<int> iv(ia, ia + 6);
// 找出不小于12的元素个数
cout << count_if(iv.begin(), iv.end(),
not1(bind2nd(less<int>(), 12)));
cout << endl;
// 令每个元素v执行(v+2)*3然后输往outite
transform(iv.begin(), iv.end(), outite,
compose1(bind2nd(multiplies<int>(), 3),
bind2nd(plus<int>(), 2)));
cout << endl;
// 将所有元素拷贝到outite
copy(iv.begin(), iv.end(), outite);
cout << endl;
// 1. 使用函数指针搭配stl算法
for_each(iv.begin(), iv.end(), print);
cout << endl;
// 2. 以修饰过的一般函数搭配stl算法
for_each(iv.begin(), iv.end(), ptr_fun(print));
cout << endl;
Int t1(3), t2(7), t3(20), t4(14), t5(68);
vector<Int> Iv;
Iv.push_back(t1);
Iv.push_back(t2);
Iv.push_back(t3);
Iv.push_back(t4);
Iv.push_back(t5);
// 3. 以修饰过的成员函数搭配stl算法
for_each(Iv.begin(), Iv.end(), mem_fun_ref(&Int::print1));
}