我认为C ++ 0x绑定要好得多,但我想在使用C ++ 0x绑定之前理解旧的bind1st和2st:
struct AAA
{
int i;
};
struct BBB
{
int j;
};
// an adaptable functor.
struct ConvertFunctor : std::binary_function<const AAA&, int, BBB>
{
BBB operator()(const AAA& aaa, int x)
{
BBB b;
b.j = aaa.i * x;
return b;
}
};
BBB ConvertFunction(const AAA& aaa, int x)
{
BBB b;
b.j = aaa.i * x;
return b;
}
class BindTest
{
public:
void f()
{
std::vector<AAA> v;
AAA a;
a.i = 0;
v.push_back(a);
a.i = 1;
v.push_back(a);
a.i = 2;
v.push_back(a);
// It works.
std::transform(
v.begin(), v.end(),
std::back_inserter(m_bbb),
std::bind(ConvertFunction, std::placeholders::_1, 100));
// It works.
std::transform(
v.begin(), v.end(),
std::back_inserter(m_bbb),
std::bind(ConvertFunctor(), std::placeholders::_1, 100));
// It doesn't compile. Why? How do I fix this code to work?
std::transform(
v.begin(), v.end(),
std::back_inserter(m_bbb),
std::bind2nd(ConvertFunctor(), 100));
std::for_each(m_bbb.begin(), m_bbb.end(),
[](const BBB& x){ printf("%d\n", x.j); });
}
private:
std::vector<BBB> m_bbb;
};
int _tmain(int argc, _TCHAR* argv[])
{
BindTest bt;
bt.f();
}
为什么不能编译第三个转换函数?如何修复此代码?
答案 0 :(得分:5)
更改
struct ConvertFunctor : std::binary_function<const AAA&, int, BBB>
{
BBB operator()(const AAA& aaa, int x)
{
为:
struct ConvertFunctor : std::binary_function<AAA, int, BBB>
{
BBB operator()(const AAA& aaa, int x) const
{
不要问我为什么,我只阅读编译错误消息。