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Coding Standards
Front Page / Sequences / Views / empty_sequence |
struct empty_sequence { // unspecified // ... };
Represents a sequence containing no elements.
#include <boost/mpl/empty_sequence.hpp>
The semantics of an expression are defined only where they differ from, or are not defined in Random Access Sequence.
In the following table, s is an instance of empty_sequence.
Expression | Semantics |
---|---|
empty_sequence | An empty Random Access Sequence. |
size<s>::type | size<s>::value == 0; see Random Access Sequence. |
typedef begin<empty_sequence>::type first; typedef end<empty_sequence>::type last; BOOST_MPL_ASSERT(( is_same<first,last> )); BOOST_MPL_ASSERT_RELATION( size<empty_sequence>::value, ==, 0 ); typedef transform_view< empty_sequence , add_pointer<_> > empty_view; BOOST_MPL_ASSERT_RELATION( size<empty_sequence>::value, ==, 0 );