The MPL Reference Manual: push_front

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::type r;

Return type:

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

Front Extensible Sequence.

Semantics:

Equivalent to

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

Postcondition:

size::value == size::value + 1~~; front::type is identical to x.~~

Complexity

Amortized constant time.

Example

typedef vector_c v;
BOOST_MPL_ASSERT_RELATION( size::value, ==, 7 );

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

BOOST_MPL_ASSERT(( equal<
      fibonacci
    , vector_c
    , equal_to<_,_>
    > ));

Boost C++ Libraries