我在做什么
三年后我开始练习c++。我需要快速、广泛地学习,所以我试图解决的这个例子对你来说可能看起来很奇怪。
我在用c++20
, gcc 10.2
.
我想做一个python 枚举函数 that
- 采取任何
container<T>
- Yields
std::tuple<int, T>
- Where
T
是容器中物品的类型
我想尝试申请蟒蛇范围作为一个论点enumerate
which
- Takes
(int start, int end, int step)
- Yields
int i
from start
to end
every step
range(不是我的代码,我只是添加了step
功能)
template <typename T>
class range_iterator;
template <typename T>
class range_impl
{
const T start_;
const T stop_;
const T step_;
public:
range_impl(T start, T stop, T step) : start_{start}, stop_{stop}, step_{step} {};
range_impl(T start, T stop) : start_{start}, stop_{stop}, step_{1} {};
range_impl(T stop) : start_{0}, stop_{stop}, step_{1} {};
range_iterator<T> begin() const
{
return range_iterator<T>{start_, step_};
}
range_iterator<T> end() const
{
return range_iterator<T>{stop_, step_};
}
};
template <typename T>
class range_iterator
{
T current_;
const T step_;
public:
range_iterator(T init, T step) : current_{init}, step_{step} {};
range_iterator<T> &operator++()
{
current_ += step_;
return *this;
}
bool operator!=(const range_iterator<T> &rhs) const
{
return current_ != rhs.current_;
}
T operator*() const
{
return current_;
}
};
template <typename T>
range_impl<T> range(const T start, const T stop, const T step)
{
return range_impl<T>(start, stop, step);
}
template <typename T>
range_impl<T> range(const T start, const T stop)
{
return range_impl<T>(start, stop);
}
template <typename T>
range_impl<T> range(const T stop)
{
return range_impl<T>(stop);
}
可以像下面这样使用
#include <iostream>
int main()
{
for(auto i: range(0, 100 2)
{
std::cout << i << std::endl;
}
}
问题代码:枚举
template <typename T>
class enumerate_iterator;
// Here, T should be a type of a container that contains type X
template <typename T>
class enumerate_impl
{
T impl;
public:
enumerate_impl<T>(T impl) : impl{impl} {/* empty */};
enumerate_iterator begin() const
{
return enumerate_iterator{impl.begin()};
}
enumerate_iterator end() const
{
return enumerate_iterator{impl.end()};
}
};
// Here, T should be a type of a iterator, I think. Confused myself.
template <typename T>
class enumerate_iterator
{
T iterator;
int i;
public:
enumerate_iterator(T iterator) : iterator{iterator}, i{0} {/* empty body */};
enumerate_iterator<T> &operator++()
{
i++;
iterator++;
return *this;
}
bool operator!=(const enumerate_iterator<T> &rhs) const
{
return iterator != rhs.iterator;
}
std::tuple operator*() const
{
return {i, *iterator};
}
};
template <typename T>
enumerate_impl<T> enumerate(T impl)
{
return enumerate_impl<T>{impl};
}
预期用途
#include <iostream>
int main()
{
for (auto &[i, j] : enumerate(range(0, 100, 2)))
{
std::cout << i << " " << j << std::endl;
}
}
出现错误(实际上有大量的编译错误,但我想在其他错误上尝试更多)。
utility.cpp:186:20: error: deduced class type 'tuple' in function return type
186 | std::tuple operator*() const
我猜这是在抱怨you didn't tell me what type the tuple contains
。但问题是我不知道什么类型T iterator
包含。我该如何告诉return type is std::tuple<int, type T contains>
?
感谢您阅读这个又长又长的问题。