From Jason Turner

[std.iterator.tags]

C++14 → C++17 2.0 KB 34 lines
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Archived: C++14 | C++17
Markdown: C++14 | C++17
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  1. tmp/tmp2i1x8oxk/{from.md → to.md} +11 -19
tmp/tmp2i1x8oxk/{from.md → to.md} RENAMED
@@ -19,26 +19,29 @@ namespace std {
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  struct bidirectional_iterator_tag: public forward_iterator_tag { };
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  struct random_access_iterator_tag: public bidirectional_iterator_tag { };
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  }
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  ```
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  For a program-defined iterator `BinaryTreeIterator`, it could be
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  included into the bidirectional iterator category by specializing the
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  `iterator_traits` template:
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  ``` cpp
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  template<class T> struct iterator_traits<BinaryTreeIterator<T>> {
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- typedef std::ptrdiff_t difference_type;
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- typedef T value_type;
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- typedef T* pointer;
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- typedef T& reference;
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- typedef bidirectional_iterator_tag iterator_category;
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  };
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  ```
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- Typically, however, it would be easier to derive `BinaryTreeIterator<T>`
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- from `iterator<bidirectional_iterator_tag,T,ptrdiff_t,T*,T&>`.
 
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  If `evolve()` is well defined for bidirectional iterators, but can be
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  implemented more efficiently for random access iterators, then the
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  implementation is as follows:
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@@ -61,18 +64,7 @@ void evolve(RandomAccessIterator first, RandomAccessIterator last,
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  random_access_iterator_tag) {
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  // more efficient, but less generic algorithm
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  }
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  ```
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- If a C++program wants to define a bidirectional iterator for some data
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- structure containing `double` and such that it works on a large memory
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- model of the implementation, it can do so with:
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-
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- ``` cpp
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- class MyIterator :
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- public iterator<bidirectional_iterator_tag, double, long, T*, T&> {
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- // code implementing ++, etc.
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- };
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- ```
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-
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- Then there is no need to specialize the `iterator_traits` template.
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  struct bidirectional_iterator_tag: public forward_iterator_tag { };
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  struct random_access_iterator_tag: public bidirectional_iterator_tag { };
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  }
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  ```
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+ [*Example 1*:
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+
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  For a program-defined iterator `BinaryTreeIterator`, it could be
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  included into the bidirectional iterator category by specializing the
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  `iterator_traits` template:
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  ``` cpp
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  template<class T> struct iterator_traits<BinaryTreeIterator<T>> {
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+ using iterator_category = bidirectional_iterator_tag;
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+ using difference_type = ptrdiff_t;
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+ using value_type = T;
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+ using pointer = T*;
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+ using reference = T&;
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  };
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  ```
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+ — *end example*]
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+
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+ [*Example 2*:
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  If `evolve()` is well defined for bidirectional iterators, but can be
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  implemented more efficiently for random access iterators, then the
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  implementation is as follows:
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  random_access_iterator_tag) {
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  // more efficient, but less generic algorithm
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  }
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  ```
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+ — *end example*]
 
 
 
 
 
 
 
 
 
 
 
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