自定义容器的STL兼容迭代器 [英] STL-compatible iterators for custom containers
问题描述
我有一个自定义的容器，我已经使用了很多年没有问题。最近我发现如果我为我的容器定义迭代器，我可以有效地使用< algorithm> 中定义的所有算法。不仅如此，似乎推力库（基本上认为CUDA版本的STL为Nvidia GPU）大量使用迭代器，我希望通过使用
I have a custom container that I have been using for many years without issues. Recently I found out that if I define iterators for my container, I can effectively use all of the algorithms defined in <algorithm>. Not only that, it seems that thrust library (basically think CUDA version of STL for Nvidia GPUs) heavily uses iterators and I am hoping that by using them I'll be able to use that library as well.
无论如何，因为这是我第一次尝试写我自己的迭代器，我想我发布我在这里要求进一步的帮助，并确保我在做什么是正确的。所以，我写了一个小数组类，支持 iterator 和 const_iterator 类。我跑了我的类与一堆不同的STL算法和所有似乎工作正常，但这并不一定意味着我有一切正确！特别是，有没有任何操作符，我错过我的迭代器？
我定义了额外的不必要的吗？另外，由于 iterator 和 const_iterator 的大部分看起来类似，有没有办法防止重复？
Anyway, since this is my first try at writing my own iterators, I thought I post what I have here to ask for further assistance and make sure what I'm doing is right. So, I wrote a little array class that supports both iterator and const_iterator classes. I ran my class with a bunch of different STL algorithms and all seem to work fine but that does not necessarily mean I've got everything right! In particular, is there any operator that I miss for my iterators?
Have I defined extra unnecessary ones? Also, since most of iterator and const_iterator look similar, is there a way to prevent duplication?
我乐意接受建议和改进：）
I'm open to suggestions and improvements :)
Live example：http://ideone.com/7YdiQY
Live example: http://ideone.com/7YdiQY
#include <cstddef>
#include <iostream>
#include <iterator>
#include <algorithm>
template<typename T>
class my_array{
T* data_;
std::size_t size_;
public:
// ---------------------------------
// Forward declaration
// ---------------------------------
class const_iterator;
// ---------------------------------
// iterator class
// ---------------------------------
class iterator: public std::iterator<std::random_access_iterator_tag, T>
{
public:
iterator(): p_(NULL) {}
iterator(T* p): p_(p) {}
iterator(const iterator& other): p_(other.p_) {}
const iterator& operator=(const iterator& other) {p_ = other.p_; return other;}
iterator& operator++() {p_++; return *this;} // prefix++
iterator operator++(int) {iterator tmp(*this); ++(*this); return tmp;} // postfix++
iterator& operator--() {p_--; return *this;} // prefix--
iterator operator--(int) {iterator tmp(*this); --(*this); return tmp;} // postfix--
void operator+=(const std::size_t& n) {p_ += n;}
void operator+=(const iterator& other) {p_ += other.p_;}
iterator operator+ (const std::size_t& n) {iterator tmp(*this); tmp += n; return tmp;}
iterator operator+ (const iterator& other) {iterator tmp(*this); tmp += other; return tmp;}
void operator-=(const std::size_t& n) {p_ -= n;}
void operator-=(const iterator& other) {p_ -= other.p_;}
iterator operator- (const std::size_t& n) {iterator tmp(*this); tmp -= n; return tmp;}
std::size_t operator- (const iterator& other) {return p_ - other.p_;}
bool operator< (const iterator& other) {return (p_-other.p_)< 0;}
bool operator<=(const iterator& other) {return (p_-other.p_)<=0;}
bool operator> (const iterator& other) {return (p_-other.p_)> 0;}
bool operator>=(const iterator& other) {return (p_-other.p_)>=0;}
bool operator==(const iterator& other) {return p_ == other.p_; }
bool operator!=(const iterator& other) {return p_ != other.p_; }
T& operator[](const int& n) {return *(p_+n);}
T& operator*() {return *p_;}
T* operator->(){return p_;}
private:
T* p_;
friend class const_iterator;
};
// ---------------------------------
// const_iterator class
// ---------------------------------
class const_iterator: public std::iterator<std::random_access_iterator_tag, T>
{
public:
const_iterator(): p_(NULL) {}
const_iterator(const T* p): p_(p) {}
const_iterator(const iterator& other): p_(other.p_) {}
const_iterator(const const_iterator& other): p_(other.p_) {}
const const_iterator& operator=(const const_iterator& other) {p_ = other.p_; return other;}
const const_iterator& operator=(const iterator& other) {p_ = other.p_; return other;}
const_iterator& operator++() {p_++; return *this;} // prefix++
const_iterator operator++(int) {const_iterator tmp(*this); ++(*this); return tmp;} // postfix++
const_iterator& operator--() {p_--; return *this;} // prefix--
const_iterator operator--(int) {const_iterator tmp(*this); --(*this); return tmp;} // postfix--
void operator+=(const std::size_t& n) {p_ += n;}
void operator+=(const const_iterator& other) {p_ += other.p_;}
const_iterator operator+ (const std::size_t& n) const {const_iterator tmp(*this); tmp += n; return tmp;}
const_iterator operator+ (const const_iterator& other) const {const_iterator tmp(*this); tmp += other; return tmp;}
void operator-=(const std::size_t& n) {p_ -= n;}
void operator-=(const const_iterator& other) {p_ -= other.p_;}
const_iterator operator- (const std::size_t& n) const {const_iterator tmp(*this); tmp -= n; return tmp;}
std::size_t operator- (const const_iterator& other) const {return p_ - other.p_;}
bool operator< (const const_iterator& other) const {return (p_-other.p_)< 0;}
bool operator<=(const const_iterator& other) const {return (p_-other.p_)<=0;}
bool operator> (const const_iterator& other) const {return (p_-other.p_)> 0;}
bool operator>=(const const_iterator& other) const {return (p_-other.p_)>=0;}
bool operator==(const const_iterator& other) const {return p_ == other.p_; }
bool operator!=(const const_iterator& other) const {return p_ != other.p_; }
const T& operator[](const int& n) const {return *(p_+n);}
const T& operator*() const {return *p_;}
const T* operator->() const {return p_;}
private:
const T* p_;
};
my_array()
: data_(NULL), size_(0)
{}
my_array(std::size_t size)
: data_(new T[size]), size_(size)
{}
my_array(const my_array<T>& other){
size_ = other.size_;
data_ = new T[size_];
for (std::size_t i = 0; i<size_; i++)
data_[i] = other.data_[i];
}
my_array(const const_iterator& first, const const_iterator& last){
size_ = last - first;
data_ = new T[size_];
for (std::size_t i = 0; i<size_; i++)
data_[i] = first[i];
}
~my_array(){
delete [] data_;
}
const my_array<T>& operator=(const my_array<T>& other){
size_ = other.size_;
data_ = new T[size_];
for (std::size_t i = 0; i<size_; i++)
data_[i] = other.data_[i];
return other;
}
const T& operator[](std::size_t idx) const {return data_[idx];}
T& operator[](std::size_t& idx) {return data_[idx];}
std::size_t size(){return size_;}
iterator begin(){ return iterator(data_); }
iterator end() { return iterator(data_+size_); }
const_iterator begin() const{ return const_iterator(data_); }
const_iterator end() const { return const_iterator(data_+size_);}
};
template<typename T>
void print(T t) {
std::cout << t << std::endl;
}
int main(){
// works!
int list [] = {1, 3, 5, 2, 4, 3, 5, 10, 10};
my_array<int> a(list, list+sizeof(list)/sizeof(int));
// works!
for (my_array<int>::const_iterator it = a.begin(), end = a.end();
it != end; ++it)
std::cout << ' ' << *it;
std::cout << std::endl;
// works!
std::for_each(a.begin(), a.end(), print<int>);
std::cout << std::endl;
// works!
my_array<int> b(a.size());
std::copy(a.begin(), a.end(), b.begin());
// works!
my_array<int>::iterator end = std::remove(a.begin(), a.end(), 5);
std::for_each(a.begin(), end, print<int>);
std::cout << std::endl;
// works!
std::random_shuffle(a.begin(), end);
std::for_each(a.begin(), end, print<int>);
std::cout << std::endl;
// works!
std::cout << "Counts of 3 in array = " << std::count(a.begin(), end, 3) << std::endl << std::endl;
// works!
std::sort(a.begin(), end);
std::for_each(a.begin(), end, print<int>);
std::cout << std::endl;
// works!
if (!std::binary_search(a.begin(), a.end(), 5))
std::cout << "Removed!" << std::endl;
return 0;
}
推荐答案
boost迭代器提供了一个框架来创建符合stl的迭代器，并适应现有
boost iterator provides a framework to create stl-compliant iterators and to adapt existing ones.
它允许您专注于功能，并生成所有必要的特性，typedefs。
It allows you to focus on the functionality and generates all necessary traits, typedefs for you.
迭代器和 const_iterator 创建时没有太多的代码重复也被支持。
iterator and const_iterator creation without much code-duplication is supported as well.
这篇关于自定义容器的STL兼容迭代器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
