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8_1_3_compose.cpp
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56 lines (48 loc) · 1.61 KB
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// file: 8compose.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);
}
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);
// 想执行v = (v+2)*3
// for_each是non-mutating algorithm，元素内容不能更改
// 所以执行后iv内容不变
for_each(iv.begin(), iv.end(),
compose1(bind2nd(multiplies<int>(), 3),
bind2nd(plus<int>(), 2)));
copy(iv.begin(), iv.end(), outite);
cout << endl;
transform(iv.begin(), iv.end(), outite,
compose1(bind2nd(multiplies<int>(), 3),
bind2nd(plus<int>(), 2)));
cout << endl;
}