push_front

Synopsis

template<
      typename Sequence
    , typename T
    >
struct push_front
{
    typedef unspecified type;
};

Description

push_front performs an insertion at the beginning of the sequence with guaranteed O(1) complexity.

Header

#include <boost/mpl/push_front.hpp>

Model of

Tag Dispatched Metafunction

Parameters

Parameter	Requirement	Description
`Sequence`	Front Extensible Sequence	A sequence to insert into.
`T`	Any type	The element to be inserted.

Expression semantics

For any Front Extensible Sequence s and arbitrary type x:

typedef push_front<s,x>::type r;

Return type: Front Extensible Sequence.

Semantics:

Return type:	Front Extensible Sequence.
Semantics:	Equivalent to typedef insert< s,begin<s>::type,x >::type r;
Postcondition:	`size<r>::value == size<s>::value + 1`; `front<r>::type` is identical to `x`.

Equivalent to

typedef insert< s,begin<s>::type,x >::type r;

Postcondition: size<r>::value == size<s>::value + 1; front<r>::type is identical to x.

Complexity

Amortized constant time.

Example

typedef vector_c<int,1,2,3,5,8,13,21> v;
BOOST_MPL_ASSERT_RELATION( size<v>::value, ==, 7 );

typedef push_front< v,integral_c<int,1> >::type fibonacci;
BOOST_MPL_ASSERT_RELATION( size<fibonacci>::value, ==, 8 );

BOOST_MPL_ASSERT(( equal< 
      fibonacci
    , vector_c<int,1,1,2,3,5,8,13,21>
    , equal_to<_,_>
    > ));