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Front Page / Sequences / Intrinsic Metafunctions / at_c

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: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 >::value), ==, 10 );
BOOST_MPL_ASSERT_RELATION( (at_c< range,10 >::value), ==, 20 );
BOOST_MPL_ASSERT_RELATION( (at_c< range,40 >::value), ==, 50 );

See also

Forward Sequence, Random Access Sequence, at, front, back