rs-core

Core utilities

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Iterator Base Classes

Core utility library by Ross Smith

#include "rs-core/iterator.hpp"
namespace RS;

Contents

• Iterator Base Classes
  • Contents
  • Iterator concepts
  • Iterator base class

Iterator concepts

template <typename I, typename V> concept ReadableIterator;
template <typename I, typename V> concept ReadableForwardIterator;
template <typename I, typename V> concept ReadableBidirectionalIterator;
template <typename I, typename V> concept ReadableRandomAccessIterator;
template <typename I, typename V> concept ReadableContiguousIterator;
template <typename I, typename V> concept WritableIterator;
template <typename I, typename V> concept WritableForwardIterator;
template <typename I, typename V> concept WritableBidirectionalIterator;
template <typename I, typename V> concept WritableRandomAccessIterator;
template <typename I, typename V> concept WritableContiguousIterator;
template <typename I, typename V> concept ReadWriteIterator;
template <typename I, typename V> concept ReadWriteForwardIterator;
template <typename I, typename V> concept ReadWriteBidirectionalIterator;
template <typename I, typename V> concept ReadWriteRandomAccessIterator;
template <typename I, typename V> concept ReadWriteContiguousIterator;

Iterator concepts compatible with specific value types. All of these require I to be an iterator of the appropriate type. ReadableIterator also requires a dereferenced iterator to be assignable to a V object; WritableIterator requires a dereferenced iterator to be assignable from a V object.

Iterator base class

template <typename I, typename CV, typename Guide> class Iterator;

This is a mixin class that can be used to easily create iterators using the CRTP pattern. In the template parameters:

• I is the iterator class being defined.
• CV is either the iterator’s value_type or const value_type depending on whether we want a mutable or constant iterator.
• Guide is a type used to indicate the intended iterator category. It can be any of:
  • One of the standard iterator category tag classes.
  • Another iterator type of the intended category.
  • A range type of the intended category.

The table below shows which operations must be defined for each category of iterator, and which are automatically generated by the mixin base class.

In this table:

• i, j are objects of the iterator type.
• v is an object of the value type.
• n is an integer.

Iterator category	Requires	Defines
Output	i=v	*i ++i i++
Input Forward	*i ++i i==j	i-> i++ i!=j i<=>j
Bidirectional	*i ++i --i i==j	i-> i++ i-- i!=j i<=>j
Random access Contiguous	*i i+=n i-j	i-> i[n] ++i i++ --i i-- i-=n i+n n+i i-n i==j i!=j i<j i>j i<=j i>=j i<=>j

Example:

class MyIterator:
public RS::Iterator<MyIterator, const int, std::forward_iterator_tag> {
public:
    const int& operator*() const;
    MyIterator& operator++();
    bool operator==(const MyIterator& i) const;
};