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< title > The MPL Reference Manual: reverse_fold</ title >
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< table class = "header" >< tr class = "header" >< td class = "header-group navigation-bar" >< span class = "navigation-group" >< a href = "./iter-fold.html" class = "navigation-link" > Prev</ a > < a href = "./reverse-iter-fold.html" class = "navigation-link" > Next</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./iter-fold.html" class = "navigation-link" > Back</ a > < a href = "./reverse-iter-fold.html" class = "navigation-link" > Along</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./iteration-algorithms.html" class = "navigation-link" > Up</ a > < a href = "../refmanual.html" class = "navigation-link" > Home</ a ></ span >< span class = "navigation-group-separator" > | </ span >< span class = "navigation-group" >< a href = "./refmanual_toc.html" class = "navigation-link" > Full TOC</ a ></ span ></ td >
< td class = "header-group page-location" >< a href = "../refmanual.html" class = "navigation-link" > Front Page</ a > / < a href = "./algorithms.html" class = "navigation-link" > Algorithms</ a > / < a href = "./iteration-algorithms.html" class = "navigation-link" > Iteration Algorithms</ a > / < a href = "./reverse-fold.html" class = "navigation-link" > reverse_fold</ a ></ td >
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< div class = "section" id = "reverse-fold" >
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< h1 >< a class = "toc-backref" href = "./iteration-algorithms.html#id1471" > reverse_fold</ a ></ h1 >
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< div class = "section" id = "id509" >
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< h3 >< a class = "subsection-title" href = "#synopsis" name = "synopsis" > Synopsis</ a ></ h3 >
< pre class = "literal-block" >
template<
typename Sequence
, typename State
, typename BackwardOp
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, typename ForwardOp = < a href = "./placeholders.html" class = "identifier" > _1</ a >
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>
struct < a href = "./reverse-fold.html" class = "identifier" > reverse_fold</ a >
{
typedef < em > unspecified</ em > type;
};
</ pre >
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< h3 >< a class = "subsection-title" href = "#description" name = "description" > Description</ a ></ h3 >
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< p > Returns the result of the successive application of binary < tt class = "literal" >< span class = "pre" > BackwardOp</ span ></ tt > to the
result of the previous < tt class = "literal" >< span class = "pre" > BackwardOp</ span ></ tt > invocation (< tt class = "literal" >< span class = "pre" > State</ span ></ tt > if it's the first call)
and every element in the range [< tt class = "literal" >< span class = "pre" >< a href = "./begin.html" class = "identifier" > begin</ a > < Sequence> ::type</ span ></ tt > , < tt class = "literal" >< span class = "pre" >< a href = "./end.html" class = "identifier" > end</ a > < Sequence> ::type</ span ></ tt > ) in
reverse order. If < tt class = "literal" >< span class = "pre" > ForwardOp</ span ></ tt > is provided, then it is applied on forward
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traversal to form the result that is passed to the first < tt class = "literal" >< span class = "pre" > BackwardOp</ span ></ tt > call.</ p >
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< h3 >< a class = "subsection-title" href = "#header" name = "header" > Header</ a ></ h3 >
< pre class = "literal-block" >
#include < < a href = "../../../../boost/mpl/reverse_fold.hpp" class = "header" > boost/mpl/reverse_fold.hpp</ a > >
</ pre >
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< div class = "section" id = "id512" >
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< h3 >< a class = "subsection-title" href = "#parameters" name = "parameters" > Parameters</ a ></ h3 >
</ div >
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< div class = "section" id = "id513" >
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< h3 >< a class = "subsection-title" href = "#parameters" name = "parameters" > Parameters</ a ></ h3 >
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< table border = "1" class = "docutils table" >
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< colgroup >
< col width = "16%" />
< col width = "33%" />
< col width = "51%" />
</ colgroup >
< thead valign = "bottom" >
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< tr >< th class = "head" > Parameter</ th >
< th class = "head" > Requirement</ th >
< th class = "head" > Description</ th >
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</ tr >
</ thead >
< tbody valign = "top" >
< tr >< td >< tt class = "literal" >< span class = "pre" > Sequence</ span ></ tt ></ td >
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< td >< a class = "reference internal" href = "./forward-sequence.html" > Forward Sequence</ a ></ td >
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< td > A sequence to iterate.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > State</ span ></ tt ></ td >
< td > Any type</ td >
< td > The initial state for the first < tt class = "literal" >< span class = "pre" > BackwardOp</ span ></ tt >
/ < tt class = "literal" >< span class = "pre" > ForwardOp</ span ></ tt > application.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > BackwardOp</ span ></ tt ></ td >
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< td > Binary < a class = "reference internal" href = "./lambda-expression.html" > Lambda Expression</ a ></ td >
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< td > The operation to be executed on backward
traversal.</ td >
</ tr >
< tr >< td >< tt class = "literal" >< span class = "pre" > ForwardOp</ span ></ tt ></ td >
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< td > Binary < a class = "reference internal" href = "./lambda-expression.html" > Lambda Expression</ a ></ td >
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< td > The operation to be executed on forward
traversal.</ td >
</ tr >
</ tbody >
</ table >
</ div >
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< div class = "section" id = "id514" >
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< h3 >< a class = "subsection-title" href = "#expression-semantics" name = "expression-semantics" > Expression semantics</ a ></ h3 >
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< p > For any < a class = "reference internal" href = "./forward-sequence.html" > Forward Sequence</ a > < tt class = "literal" >< span class = "pre" > s</ span ></ tt > , binary < a class = "reference internal" href = "./lambda-expression.html" > Lambda Expression</ a > < tt class = "literal" >< span class = "pre" > backward_op</ span ></ tt > and < tt class = "literal" >< span class = "pre" > forward_op</ span ></ tt > ,
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and arbitrary type < tt class = "literal" >< span class = "pre" > state</ span ></ tt > :</ p >
< pre class = "literal-block" >
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typedef < a href = "./reverse-fold.html" class = "identifier" > reverse_fold</ a > < s,state,backward_op > ::type t;
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</ pre >
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< table class = "docutils field-list" frame = "void" rules = "none" >
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< col class = "field-name" />
< col class = "field-body" />
< tbody valign = "top" >
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< tr class = "field" >< th class = "field-name" > Return type:</ th >< td class = "field-body" >< p class = "first" > A type</ p >
</ td >
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</ tr >
< tr class = "field" >< th class = "field-name" > Semantics:</ th >< td class = "field-body" >< p class = "first" > Equivalent to</ p >
< pre class = "last literal-block" >
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typedef < a href = "./lambda.html" class = "identifier" > lambda</ a > < backward_op> ::type op;
typedef < a href = "./reverse-iter-fold.html" class = "identifier" > reverse_iter_fold</ a > <
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s
, state
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, apply_wrap2< op, < a href = "./placeholders.html" class = "identifier" > _1</ a > , < a href = "./deref.html" class = "identifier" > deref</ a > < < a href = "./placeholders.html" class = "identifier" > _2</ a > > >
> ::type t;
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</ pre >
</ td >
</ tr >
</ tbody >
</ table >
<!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
< pre class = "literal-block" >
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typedef < a href = "./reverse-fold.html" class = "identifier" > reverse_fold</ a > < s,state,backward_op,forward_op > ::type t;
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</ pre >
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< table class = "docutils field-list" frame = "void" rules = "none" >
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< col class = "field-name" />
< col class = "field-body" />
< tbody valign = "top" >
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< tr class = "field" >< th class = "field-name" > Return type:</ th >< td class = "field-body" >< p class = "first" > A type.</ p >
</ td >
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</ tr >
< tr class = "field" >< th class = "field-name" > Semantics:</ th >< td class = "field-body" >< p class = "first" > Equivalent to</ p >
< pre class = "last literal-block" >
typedef < a href = "./reverse-fold.html" class = "identifier" > reverse_fold</ a > <
Sequence
, < a href = "./fold.html" class = "identifier" > fold</ a > < s,state,forward_op> ::type
, backward_op
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> ::type t;
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</ pre >
</ td >
</ tr >
</ tbody >
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< div class = "section" id = "id515" >
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< h3 >< a class = "subsection-title" href = "#complexity" name = "complexity" > Complexity</ a ></ h3 >
< p > Linear. Exactly < tt class = "literal" >< span class = "pre" >< a href = "./size.html" class = "identifier" > size</ a > < s> ::value</ span ></ tt > applications of < tt class = "literal" >< span class = "pre" > backward_op</ span ></ tt > and < tt class = "literal" >< span class = "pre" > forward_op</ span ></ tt > .</ p >
</ div >
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< div class = "section" id = "id516" >
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< h3 >< a class = "subsection-title" href = "#example" name = "example" > Example</ a ></ h3 >
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< p > Remove non-negative elements from a sequence < a class = "footnote-reference" href = "#reverse-fold-note" id = "id517" > [2]</ a > .</ p >
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< pre class = "literal-block" >
typedef < a href = "./list-c.html" class = "identifier" > list_c</ a > < int,5,-1,0,-7,-2,0,-5,4> numbers;
typedef < a href = "./list-c.html" class = "identifier" > list_c</ a > < int,-1,-7,-2,-5> negatives;
typedef < a href = "./reverse-fold.html" class = "identifier" > reverse_fold</ a > <
numbers
, < a href = "./list-c.html" class = "identifier" > list_c</ a > < int>
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, < a href = "./if.html" class = "identifier" > if_</ a > < < a href = "./less.html" class = "identifier" > less</ a > < < a href = "./placeholders.html" class = "identifier" > _2</ a > ,< a href = "./int.html" class = "identifier" > int_</ a > < 0> > , < a href = "./push-front.html" class = "identifier" > push_front</ a > < < a href = "./placeholders.html" class = "identifier" > _1</ a > ,< a href = "./placeholders.html" class = "identifier" > _2</ a > ,> , < a href = "./placeholders.html" class = "identifier" > _1</ a > >
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> ::type result;
< a href = "./assert.html" class = "identifier" > BOOST_MPL_ASSERT</ a > (( < a href = "./equal.html" class = "identifier" > equal</ a > < negatives,result > ));
</ pre >
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< table class = "docutils footnote" frame = "void" id = "reverse-fold-note" rules = "none" >
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< colgroup >< col class = "label" />< col /></ colgroup >
< tbody valign = "top" >
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< tr >< td class = "label" >< a class = "fn-backref" href = "#id517" > [2]</ a ></ td >< td > See < tt class = "literal" >< span class = "pre" >< a href = "./remove-if.html" class = "identifier" > remove_if</ a ></ span ></ tt > for a more compact way to do this.</ td ></ tr >
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</ tbody >
</ table >
</ div >
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< div class = "section" id = "id518" >
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< h3 >< a class = "subsection-title" href = "#see-also" name = "see-also" > See also</ a ></ h3 >
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< p >< a class = "reference internal" href = "./algorithms.html" > Algorithms</ a > , < a class = "reference internal" href = "./fold.html" > fold</ a > , < a class = "reference internal" href = "./reverse-iter-fold.html" > reverse_iter_fold</ a > , < a class = "reference internal" href = "./iter-fold.html" > iter_fold</ a ></ p >
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<!-- Algorithms/Iteration Algorithms//reverse_iter_fold -->
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< td >< div class = "copyright-footer" >< div class = "copyright" > Copyright © 2001-2009 Aleksey Gurtovoy and David Abrahams</ div >
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