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Added docs for iterator category and traversal manipulation tools.

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Andrey Semashev 2014-08-24 01:55:25 +04:00
parent a569c97969
commit 82779f78ec
1 changed files with 103 additions and 3 deletions
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106
doc/quickbook/utilities.qbk
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@ -49,11 +49,40 @@ proxy references or return the pointee by value. When that
information is needed, call on `indirect_reference`.
Both of these templates are essential to the correct functioning of
[link indirecct `indirect_iterator`].
[link boost_iterator.indirect `indirect_iterator`].
[h2 `minimum_category`]
`minimum_category` takes two iterator categories or two iterator traversal tags
and returns the one that is the weakest (i.e. least advanced). For example:
static_assert(
is_same<
minimum_category<
std::forward_iterator_tag,
std::random_access_iterator_tag
>::type,
std::forward_iterator_tag
>::value,
"Unexpected minimum_category result"
);
[h2 Iterator category and traversal tags manipulation]
The library provides several utilities to simplify conversions between iterator categories
and traversal tags:
* `iterator_category_to_traversal<C>::type` - the metafunction takes an iterator category `C` and returns
the corresponding traversal tag.
* `iterator_traversal<T>::type` - a shorthand for `iterator_category_to_traversal<iterator_category<T>::type>::type`.
* `pure_traversal_tag<T>::type` - the metafunction takes a tag `T` which derives from one of the iterator traversal tags
and returns that traversal tag. `T` may also derive from other tags describing the iterator (e.g. whether this is a `const`-iterator
or not), these additional tags are not considered.
* `pure_iterator_traversal<T>::type` - a shorthand for `pure_traversal_tag<iterator_traversal<T>::type>::type`.
[h2 Reference]
[h3 `pointeee`]
[h3 `pointee`]
template <class Dereferenceable>
struct pointee
@ -110,6 +139,77 @@ Both of these templates are essential to the correct functioning of
else
std::iterator_traits<Dereferenceable>::reference
[h3 `minimum_category`]
template <typename C1, typename C2>
struct minimum_category
{
typedef /* see below */ type;
};
[*Requires:] Both `C1` and `C2` shall be standard iterator categories or
iterator traversal tags.
`type` is determined according to the following algorithm, where `c1` is an
object of type `C1` and `c2` is an object of type `C2`:
if (c1 is convertible to c2)
return C2;
else
return C1;
[note The above definition relies on the fact that the more restricting categories
and traversal tags are convertible to the less restricting ones.]
[h3 `iterator_category_to_traversal`]
template <typename C>
struct iterator_category_to_traversal
{
typedef /* see below */ type;
};
[*Requires:] `C` shall be a standard iterator category or an
iterator traversal tag.
If `C` is an iterator traversal tag or convertible to one, `type` equivalent to `C`.
Otherwise, `type` is defined to the closest iterator traversal tag matching `C`.
[h3 `iterator_traversal`]
template <typename Iterator>
struct iterator_traversal
{
typedef typename iterator_category_to_traversal<
typename iterator_category<Iterator>::type
>::type type;
};
[*Requires:] `Iterator` shall be an iterator.
[h3 `pure_traversal_tag`]
template <typename T>
struct pure_traversal_tag
{
typedef /* see below */ type;
};
[*Requires:] `T` shall be convertible to an iterator traversal tag.
`type` is defined to be the most advanced traversal tag `Tag` so that `T` is convertible to `Tag`.
[h3 `pure_iterator_traversal`]
template <typename Iterator>
struct pure_iterator_traversal
{
typedef typename pure_traversal_tag<
typename iterator_traversal<Iterator>::type
>::type type;
};
[*Requires:] `Iterator` shall be an iterator.
[endsect]
@ -221,4 +321,4 @@ Iterator Traversal Concepts
[endsect]
[endsect]
[endsect]