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< html > < head > < title > boost::mpl::empty< / title >
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< h1 > < a href = "../Table_of_Contents.html" > < img src = "../mpl_logo.jpg" alt = "[Home]" border = 0 align = "right" > < / a > empty< / h1 > < h3 > Synopsis< / h3 >
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template<
typename Sequence
>
struct empty
{
typedef < em > unspecified< / em > type;
};
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< h3 > Description< / h3 >
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Returns an < a href = "../Integral_Constant.html" > Integral Constant< / a > < code > c< / code > such that < code > c::value == true< / code > if and only if the sequence is empty.
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< h3 > Definition< / h3 >
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< pre >
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#include "< a href = "../../../../../boost/mpl/empty.hpp" > boost/mpl/empty.hpp< / a > "
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< h3 > Parameters< / h3 >
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< tr > < th > Parameter < / th > < th > Requirement < / th > < th > Description < / th > < / tr >
< tr > < td > < code > Sequence< / code > < / td > < td > A model of < a href = "../Sequence.html" > Sequence< / a > < / td > < td > < / td > < / tr >
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< h3 > Expression semantics< / h3 >
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< tr > < th > Expression < / th > < th > Expression type < / th > < th > Precondition < / th > < th > Semantics < / th > < th > Postcondition < / th > < / tr >
< tr > < td > < code > typedef empty< Sequence> ::type c;< / code > < / td > < td > A model of < code > bool< / code > < a href = "../Integral_Constant.html" > Integral Constant< / a > < / td > < td > < / td > < td > Equivalent to < code > typedef is_same< begin< Sequence> ::type,end< Sequence> ::type > ::type c;< / code > < / td > < td > < / td > < / tr >
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< h3 > Complexity< / h3 >
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Amortized constant time.
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< h3 > Example< / h3 >
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typedef range_c< int,0,0> empty_range;
typedef list< long,float,double> types;
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BOOST_STATIC_ASSERT(empty< empty_range> ::value)
BOOST_STATIC_ASSERT(!empty< types> ::value)
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< h3 > See also< / h3 >
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< a href = "../Sequence.html" > Sequence< / a > , < code > < a href = "../Reference/size.html" > size< / a > < / code > , < code > < a href = "../Reference/begin.html" > begin< / a > < / code > , < code > < a href = "../Reference/end.html" > end< / a > < / code >
< p > < hr >
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< a href = "../Table_of_Contents.html" > Table of Contents< / a > < br > Last edited July 17, 2002 3:52 am< / body > < / html >
