...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
bimap
instantiations comprise
two side views and an view of the relation specified at compile time. Each
view allows read-write access to the elements contained in a definite manner,
mathing an STL container signature.
Views are not isolated objects and so cannot be constructed on their own;
rather they are an integral part of a bimap
.
The name of the view class implementation proper is never directly exposed
to the user, who has access only to the associated view type specifier.
Insertion and deletion of elements are always performed through the appropriate
interface of any of the three views of the bimap
;
these operations do, however, have an impact on all other views as well:
for instance, insertion through a given view may fail because there exists
another view that forbids the operation in order to preserve its invariant
(such as uniqueness of elements). The global operations performed jointly
in the any view can be reduced to six primitives:
The last two primitives deserve some further explanation: in order to guarantee
the invariants associated to each view (e.g. some definite ordering) elements
of a bimap
are not mutable.
To overcome this restriction, the views expose member functions for updating
and modifying, which allows for the mutation of elements in a controlled
fashion.
Some member functions of a view interface are implemented by global primitives
from the above list. The complexity of these operations thus depends on
all views of a given bimap
,
not just the currently used view.
In order to establish complexity estimates, a view is characterised by its complexity signature, consisting of the following associated functions on the number of elements:
c(n)
:
copying
i(n)
:
insertion
h(n)
:
hinted insertion
d(n)
:
deletion
r(n)
:
replacement
m(n)
:
modifying
If the collection type of the relation is left_based
or right_based
, and we
use an l
subscript to denote
the left view and an r
for the right view, then the insertion of an element in such a container
is of complexity O(i_l(n)+i_r(n))
,
where n is the number of elements. If the collection type of relation is
not side-based, then there is an additional term to add that is contributed
by the collection type of relation view. Using a
to denote the above view, the complexity of insertion will now be O(i_l(n)+i_r(n)+i_a(n))
.
To abbreviate the notation, we adopt the following definitions:
C(n) = c_l(n) + c_r(n) [ + c_a(n) ]
I(n) = i_l(n) + i_r(n) [ + i_a(n) ]
H(n) = h_l(n) + h_r(n) [ + h_a(n) ]
D(n) = d_l(n) + d_r(n) [ + d_a(n) ]
R(n) = r_l(n) + r_r(n) [ + r_a(n) ]
M(n) = m_l(n) + m_r(n) [ + m_a(n) ]
Set type specifiers are passed as instantiation arguments to bimap
and provide the information needed
to incorporate the corresponding views. Currently, Boost.Bimap provides
the collection type specifiers. The side collection type
specifiers define the constraints of the two map views of the bimap. The
collection type of relation specifier defines the
main set view constraints. If left_based
(the default parameter) or right_based
is used, then the collection type of relation will be based on the left
or right collection type correspondingly.
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Collection type of relation |
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Tags are just conventional types used as mnemonics for the types stored
in a bimap
. Boost.Bimap
uses the tagged idiom to let the user specify this tags.
namespace boost { namespace bimaps { template< class Type, typename Tag > struct tagged; // bimap template class template < class LeftCollectionType, class RightCollectionType, class AdditionalParameter_1 = detail::not_specified, class AdditionalParameter_2 = detail::not_specified > class bimap - implementation defined { : public SetView } - { public: // Metadata typedef -unspecified- left_tag; typedef -unspecified- left_map; typedef -unspecified- right_tag; typedef -unspecified- right_map; // Shortcuts // typedef -side-_map::-type- -side-_-type-; typedef -unspecified- info_type; // Map views left_map left; right_map right; // Constructors bimap(); template< class InputIterator > bimap(InputIterator first,InputIterator last); bimap(const bimap &); bimap& operator=(const bimap& b); // Projection of iterators template< class IteratorType > left_iterator project_left(IteratorType iter); template< class IteratorType > left_const_iterator project_left(IteratorType iter) const; template< class IteratorType > right_iterator project_right(IteratorType iter); template< class IteratorType > right_const_iterator project_right(IteratorType iter) const; template< class IteratorType > iterator project_up(IteratorType iter); template< class IteratorType > const_iterator project_up(IteratorType iter) const; // Support for tags template< class Tag > struct map_by; template< class Tag > map_by<Tag>::type by(); template< class Tag > const map_by<Tag>::type & by() const; template< class Tag, class IteratorType > map_by<Tag>::iterator project(IteratorType iter); template< class Tag, class IteratorType > map_by<Tag>::const_iterator project(IteratorType iter) const }; } // namespace bimap } // namespace boost
This is the main component of Boost.Bimap.
In the descriptions of the operations of bimap
,
we adopt the scheme outlined in the complexity signature section.
bimap
is instantiated
with the following types:
left_tag, right_tag
Tags for each side of the bimap. If the user has not specified any tag the tags default to
member_at::left
andmember_at::right
.
left_key_type, right_key_type
Key type of each side. In a
bimap<A,B>
left_key_type
isA
andright_key_type
isB
. If there are tags, it is better to use:Bimap::map_by<Tag>::key_type
.
left_data_type, right_data_type
Data type of each side. In a bimap<A,B> left_key_type is B and right_key_type is A. If there are tags, it is better to use:
Bimap::map_by<Tag>::data_type
.
left_value_type, right_value_type
Value type used for the views. If there are tags, it is better to use:
Bimap::map_by<Tag>::value_type
.
left_iterator, right_iterator left_const_iterator, right_const_iterator
Iterators of the views. If there are tags, it is better to use:
Bimap::map_by<Tag>::iterator
andBimap::map_by<Tag>::const_iterator
left_map, right_map
Map view type of each side. If there are tags, it is better to use:
Bimap::map_by<Tag>::type
.
bimap();
bimap
.
template<typename InputIterator> bimap(InputIterator first,InputIterator last);
InputIterator
is a model of Input Iterator over elements of type relation
or a type convertible
to relation
. last
is reachable from first
.
bimap
and fills it with the elements
in the range [first,last)
. Insertion of each element may or
may not succeed depending on acceptance by the collection types of
the bimap
.
[first,last)
.
bimap(const bimap & x);
*this ==
x
. The order of the views
of the bimap
is preserved
as well.
~bimap()
bimap
and all the elements contained.
The order in which the elements are destroyed is not specified.
bimap& operator=(const bimap& x);
bimap
with copies from x.
*this==x
. The order on the views of the
bimap
is preserved
as well.
*this
.
ctor_args_list
do not throw.
Given a bimap
with views
v1 and v2, we say than an v1-iterator it1 and an v2-iterator it2 are
equivalent if:
it1 ==
i1.end()
AND it2 ==
i2.end()
,
it1
and it2
point to the same element.
template< class IteratorType > left_iterator project_left(IteratorType iter); template< class IteratorType > left_const_iterator project_left(IteratorType iter) const;
IteratorType
is a bimap view iterator. it is a valid iterator of some view of
*this
(i.e. does not refer to some other bimap
.)
it
.
template< class IteratorType > right_iterator project_right(IteratorType iter); template< class IteratorType > right_const_iterator project_right(IteratorType iter) const;
IteratorType
is a bimap view iterator. it is a valid iterator of some view of
*this
(i.e. does not refer to some other bimap
.)
it
.
template< class IteratorType > iterator project_up(IteratorType iter); template< class IteratorType > const_iterator project_up(IteratorType iter) const;
IteratorType
is a bimap view iterator. it is a valid iterator of some view of
*this
(i.e. does not refer to some other bimap
.)
it
.
template< class Tag > struct map_by;
map_by<Tag>::type
yields the type of the map
view tagged with Tag
.
map_by<Tag>::
-type
name- is the same as map_by<Tag>::type::
-type name-.
Tag
is a valid user defined name of the bimap.
template< class Tag > map_by<Tag>::type by(); template< class Tag > const map_by<Tag>::type & by() const;
Tag
is a valid user defined name of the bimap.
Tag
held by *this
.
template< class Tag, class IteratorType > map_by<Tag>::iterator project(IteratorType iter); template< class Tag, class IteratorType > map_by<Tag>::const_iterator project(IteratorType iter) const
Tag
is a valid user defined name of the bimap. IteratorType
is a bimap view iterator. it is a valid iterator of some view of
*this
(i.e. does not refer to some other bimap
.)
Tag
held by *this
.
A bimap
can be archived
and retrieved by means of Boost.Serialization. Boost.Bimap does
not expose a public serialisation interface, as this is provided by Boost.Serialization
itself. Both regular and XML archives are supported.
Each of the set specifications comprising a given bimap
contributes its own preconditions as well as guarantees on the retrieved
containers. In describing these, the following concepts are used. A type
T
is serializable
(resp. XML-serializable) if any object of type T
can be saved to an output archive (XML archive) and later retrieved from
an input archive (XML archive) associated to the same storage. If x
' of type T
is loaded from the serialization information saved from another object
x, we say that x' is a restored copy of x. Given
a Binary
Predicate Pred
over (T, T)
, and objects p
and q
of type Pred
, we say that q
is serialization-compatible with p
if
p(x,y) == q(x
',y
')
for every x
and y
of type T
and x
' and y
' being restored copies of x
and y
,
respectively.
Operation: saving of a bimap b
to an output archive (XML archive) ar.
b
. If an exception
is thrown, ar may be left in an inconsistent state.
Operation: loading of a bimap
m' from an input archive (XML
archive) ar.
b
' can impose other requirements.