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set

Description

set is a variadic, associative, extensible sequence of types that supports constant-time insertion and removal of elements, and testing for membership. A set may contain at most one element for each key.

Header

Sequence form Header
Variadic #include <boost/mpl/set.hpp>
Numbered #include <boost/mpl/set/setn.hpp>

Model of

Expression semantics

In the following table, s is an instance of set, pos is an iterator into s, and x, k, and t1,t2,... tn is a set of unique arbitrary types. [Note: See below for an example of how to construct a set from a list of potentially non-unique types — end note]

Expression Semantics
set<t1,t2,... tn>
setn<t1,t2,... tn>
set of elements t1,t2,... tn; see Variadic Sequence.
set<t1,t2,... tn>::type
setn<t1,t2,... tn>::type
Identical to setn<t1,t2,... tn>; see Variadic Sequence.
begin<s>::type An iterator pointing to the beginning of s; see Associative Sequence.
end<s>::type An iterator pointing to the end of s; see Associative Sequence.
size<s>::type The size of s; see Associative Sequence.
empty<s>::type A boolean Integral Constant c such that c::value == true if and only if s is empty; see Associative Sequence.
front<s>::type The first element in s; see Associative Sequence.
has_key<s,k>::type A boolean Integral Constant c such that c::value == true if and only if there is one or more elements with the key k in s; see Associative Sequence.
count<s,k>::type The number of elements with the key k in s; see Associative Sequence.
order<s,k>::type A unique unsigned Integral Constant associated with the key k in s; see Associative Sequence.
at<s,k>::type
at<s,k,def>::type
The element associated with the key k in s; see Associative Sequence.
key_type<s,x>::type Identical to x; see Associative Sequence.
value_type<s,x>::type Identical to x; see Associative Sequence.
insert<s,x>::type

A new set equivalent to s except that

at< t, key_type<s,x>::type >::type

is identical to value_type<s,x>::type.

insert<s,pos,x>::type Equivalent to insert<s,x>::type; pos is ignored.
erase_key<s,k>::type A new set equivalent to s except that has_key<t, k>::value == false.
erase<s,pos>::type Equivalent to erase<s, deref<pos>::type >::type.
clear<s>::type An empty set; see clear.

Example

Basic set invariants:

typedef set< int,long,double,int_<5> > s;

BOOST_MPL_ASSERT_RELATION( size<s>::value, ==, 4 );
BOOST_MPL_ASSERT_NOT(( empty<s> ));

BOOST_MPL_ASSERT(( is_same< at<s,int>::type, int > ));
BOOST_MPL_ASSERT(( is_same< at<s,long>::type, long > ));
BOOST_MPL_ASSERT(( is_same< at<s,int_<5> >::type, int_<5> > ));
BOOST_MPL_ASSERT(( is_same< at<s,char>::type, void_ > ));

Constructing a set from a list of potentially non-unique types:

typedef fold<
      vector<int,int,long,long>
    , set0<>
    , insert<_1,_2>
    >::type s;

BOOST_MPL_ASSERT_RELATION( size<s>::value, ==, 2 );

See also

Sequences, Variadic Sequence, Associative Sequence, Extensible Associative Sequence, set_c, map, vector