at_c

Synopsis

template<
      typename Sequence
    , long n
    >
struct at_c
{
    typedef unspecified type;
};

Description

Returns a type identical to the nth element from the beginning of the sequence. at_c<Sequence,n>::type is a shorcut notation for at< Sequence, long_<n> >::type.

Header

#include <boost/mpl/at.hpp>

Parameters

Parameter	Requirement	Description
`Sequence`	Forward Sequence	A sequence to be examined.
`n`	A compile-time integral constant	An offset from the beginning of the sequence specifying the element to be retrieved.

Expression semantics

typedef at_c<Sequence,n>::type t;

Return type:

Return type:	A type
Precondition:	`0 <= n < size<Sequence>::value`
Semantics:	Equivalent to typedef at< Sequence, long_<n> >::type t;

A type

Precondition:

0 <= n < size<Sequence>::value

Semantics:

Equivalent to

typedef at< Sequence, long_<n> >::type t;

Complexity

Sequence archetype	Complexity
Forward Sequence	Linear.
Random Access Sequence	Amortized constant time.

Example

typedef range_c<long,10,50> range;
BOOST_MPL_ASSERT_RELATION( (at_c< range,0 >::type::value), ==, 10 );
BOOST_MPL_ASSERT_RELATION( (at_c< range,10 >::type::value), ==, 20 );
BOOST_MPL_ASSERT_RELATION( (at_c< range,40 >::type::value), ==, 50 );

Boost C++ Libraries