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fusion: merge of associative iterators/views and the new fold interface

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[SVN r58618]
This commit is contained in:
Christopher Schmidt
2010-01-01 22:00:21 +00:00
parent b605617c4f
commit cda74605fc
379 changed files with 28481 additions and 2185 deletions
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36
doc/extension.qbk
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@ -145,15 +145,15 @@ our iterator's tag type.
The implementation itself is pretty simple, it just uses 2 partial specializations to
provide the type of the 2 different members of `example_struct`, based on the index of the iterator.
To understand how `value_of_impl` is used by the library we will look at the implementation of __value_of__:
To understand how `value_of_impl` is used by the library we will look at the implementation of __result_of_value_of__:
template <typename Iterator>
struct __value_of__
struct value_of
: extension::value_of_impl<typename detail::tag_of<Iterator>::type>::
template apply<Iterator>
{};
So __value_of__ uses __tag_dispatching__ to select an __mpl_metafunction_class__
So __result_of_value_of__ uses __tag_dispatching__ to select an __mpl_metafunction_class__
to provide its functionality. You will notice this pattern throughout the
implementation of Fusion.
@ -216,7 +216,7 @@ To see how `deref_impl` is used, lets have a look at the implementation of __der
}
So again __result_of_deref__ uses __tag_dispatching__ in exactly the
same way as the __value_of__ implementation. The runtime functionality used
same way as the __result_of_value_of__ implementation. The runtime functionality used
by __deref__ is provided by the `call` static function of the selected
__mpl_metafunction_class__.
@ -227,14 +227,14 @@ bit of metaprogramming to return `const` references if the underlying sequence
is const.
[note Although there is a fair amount of left to do to produce a fully fledged
Fusion sequence, __value_of__ and __deref__ illustrate all the signficant concepts
Fusion sequence, __result_of_value_of__ and __deref__ illustrate all the signficant concepts
required. The remainder of the process is very repetitive, simply requiring
implementation of a suitable `xxxx_impl` for each feature `xxxx`.
]
[heading Implementing the remaining iterator functionality]
Ok, now we have seen the way __value_of__ and __deref__ work, everything else will work
Ok, now we have seen the way __result_of_value_of__ and __deref__ work, everything else will work
in pretty much the same way. Lets start with forward iteration,
by providing a `next_impl`:
@ -317,14 +317,15 @@ is provided in the example code.
For our __random_access_sequence__ we will also need to implement `size_impl`,
`value_at_impl` and `at_impl`.
[heading Enabling our type as an associative container]
[heading Enabling our type as an associative sequence]
In order for `example_struct` to serve as an associative container,
we need to enable 3 lookup features, __at_key__, __value_at_key__ and __has_key__.
We also need to provide an implementation of the `is_associative` trait
so that our sequence can be correctly identified as an associative container.
In order for `example_struct` to serve as an associative forward sequence,
we need to adapt the traversal category of our sequence and our iterator
accordingly and enable 3 intrinsic sequence lookup features, __at_key__,
__value_at_key__ and __has_key__. We also need to enable 3 iterator lookup
features, __result_of_key_of__, __result_of_value_of_data__ and __deref_data__.
To implement `at_key_impl` we need to associate the `fields::age` and `fields::age`
To implement `at_key_impl` we need to associate the `fields::name` and `fields::age`
types described in the __quick_start__ guide with the appropriate members of `example_struct`.
Our implementation is as follows:
@ -369,15 +370,14 @@ Its all very similar to the implementations we've seen previously,
such as `deref_impl` and `value_of_impl`. Instead of identifying
the members by index or position, we are now selecting them using
the types `fields::name` and `fields::age`. The implementations of
`value_at_key_impl` and `has_key_impl` are equally straightforward,
and are provided in the example code, along with an implementation
of `is_associative_impl`.
the other functions are equally straightforward, and are provided in
the example code.
[heading Summary]
We've now worked through the entire process for adding a new random
access sequence and we've also enabled our type to serve as an associative
container. The implementation was slightly longwinded, but followed
sequence. The implementation was slightly longwinded, but followed
a simple repeating pattern.
The support for `std::pair`, __mpl__ sequences, and `boost::array` all
@ -467,6 +467,10 @@ The user must the implement the key expressions required by their iterator type.
[[`iterator::template distance<It1, It2>::call(it1, it2)`][The distance between iterator `it1` and `it2`][None]]
[[`iterator::template equal_to<It1, It2>::type`][The distance between iterators of type `It1` and `It2`][`boost::same_type<It1, It2>::type`]]
[[`iterator::template equal_to<It1, It2>::call(it1, it2)`][The distance between iterators `it1` and `it2`][`boost::same_type<It1, It2>::type()`]]
[[`iterator::template key_of<It>::type`][The key type associated with the element from `It`][None]]
[[`iterator::template value_of_data<It>::type`][The type of the data property associated with the element from `It`][None]]
[[`iterator::template deref_data<It>::type`][The type that will be returned by dereferencing the data property of the element from `It`][None]]
[[`iterator::template deref_data<It>::call(it)`][Deferences the data property associated with the element referenced by `it`][None]]
]
[heading Header]