2007-11-06 12:13:52 +00:00
< html >
< head >
< meta http-equiv = "Content-Type" content = "text/html; charset=ISO-8859-1" >
< title > fold< / title >
2007-11-07 03:46:23 +00:00
< link rel = "stylesheet" href = "../../../../../../../../doc/html/boostbook.css" type = "text/css" >
2007-11-06 12:13:52 +00:00
< meta name = "generator" content = "DocBook XSL Stylesheets V1.66.1" >
< link rel = "start" href = "../../../../index.html" title = "Chapter<65> 1.<2E> Fusion 2.0" >
< link rel = "up" href = "../functions.html" title = "Functions" >
< link rel = "prev" href = "../functions.html" title = "Functions" >
< link rel = "next" href = "accumulate.html" title = "accumulate" >
< / head >
< body bgcolor = "white" text = "black" link = "#0000FF" vlink = "#840084" alink = "#0000FF" >
< table cellpadding = "2" width = "100%" > < tr >
< td valign = "top" > < img alt = "Boost C++ Libraries" width = "277" height = "86" src = "../../../../../../../../boost.png" > < / td >
< td align = "center" > < a href = "../../../../../../../../index.htm" > Home< / a > < / td >
< td align = "center" > < a href = "../../../../../../../libraries.htm" > Libraries< / a > < / td >
< td align = "center" > < a href = "../../../../../../../../people/people.htm" > People< / a > < / td >
< td align = "center" > < a href = "../../../../../../../../more/faq.htm" > FAQ< / a > < / td >
< td align = "center" > < a href = "../../../../../../../../more/index.htm" > More< / a > < / td >
< / tr > < / table >
< hr >
< div class = "spirit-nav" >
< a accesskey = "p" href = "../functions.html" > < img src = "../../../../../../../../doc/html/images/prev.png" alt = "Prev" > < / a > < a accesskey = "u" href = "../functions.html" > < img src = "../../../../../../../../doc/html/images/up.png" alt = "Up" > < / a > < a accesskey = "h" href = "../../../../index.html" > < img src = "../../../../../../../../doc/html/images/home.png" alt = "Home" > < / a > < a accesskey = "n" href = "accumulate.html" > < img src = "../../../../../../../../doc/html/images/next.png" alt = "Next" > < / a >
< / div >
< div class = "section" lang = "en" >
< div class = "titlepage" > < div > < div > < h5 class = "title" >
< a name = "fusion.algorithm.iteration.functions.fold" > < / a > < a href = "fold.html" title = "fold" > fold< / a > < / h5 > < / div > < / div > < / div >
< a name = "fusion.algorithm.iteration.functions.fold.description" > < / a > < h6 >
2007-11-07 03:46:23 +00:00
< a name = "id575528" > < / a >
2007-11-06 12:13:52 +00:00
< a href = "fold.html#fusion.algorithm.iteration.functions.fold.description" > Description< / a >
< / h6 >
< p >
For a sequence < tt class = "computeroutput" > < span class = "identifier" > Seq< / span > < / tt > , initial
state, and binary function object or function pointer < tt class = "computeroutput" > < span class = "identifier" > f< / span > < / tt > ,
fold repeatedly applies binary < tt class = "computeroutput" > < span class = "identifier" > f< / span > < / tt >
to each element of < tt class = "computeroutput" > < span class = "identifier" > Seq< / span > < / tt >
and the previous state.
< / p >
< a name = "fusion.algorithm.iteration.functions.fold.synopsis" > < / a > < h6 >
2007-11-07 03:46:23 +00:00
< a name = "id575608" > < / a >
2007-11-06 12:13:52 +00:00
< a href = "fold.html#fusion.algorithm.iteration.functions.fold.synopsis" > Synopsis< / a >
< / h6 >
< pre class = "programlisting" >
< span class = "keyword" > template< / span > < span class = "special" > < < / span >
< span class = "keyword" > typename< / span > < span class = "identifier" > Sequence< / span > < span class = "special" > ,< / span >
< span class = "keyword" > typename< / span > < span class = "identifier" > State< / span > < span class = "special" > ,< / span >
< span class = "keyword" > typename< / span > < span class = "identifier" > F< / span >
< span class = "special" > > < / span >
< span class = "keyword" > typename< / span > < a href = "../metafunctions/fold.html" title = "fold" > < tt class = "computeroutput" > < span class = "identifier" > result_of< / span > < span class = "special" > ::< / span > < span class = "identifier" > fold< / span > < / tt > < / a > < span class = "special" > < < / span > < span class = "identifier" > Sequence< / span > < span class = "special" > ,< / span > < span class = "identifier" > State< / span > < span class = "special" > ,< / span > < span class = "identifier" > F< / span > < span class = "special" > > ::< / span > < span class = "identifier" > type< / span > < span class = "identifier" > fold< / span > < span class = "special" > (< / span >
< span class = "identifier" > Sequence< / span > < span class = "special" > & < / span > < span class = "identifier" > seq< / span > < span class = "special" > ,< / span > < span class = "identifier" > State< / span > < span class = "keyword" > const< / span > < span class = "special" > & < / span > < span class = "identifier" > initial_state< / span > < span class = "special" > ,< / span > < span class = "identifier" > F< / span > < span class = "keyword" > const< / span > < span class = "special" > & < / span > < span class = "identifier" > f< / span > < span class = "special" > );< / span >
< / pre >
< div class = "table" >
2007-11-07 03:46:23 +00:00
< a name = "id575867" > < / a > < p class = "title" > < b > Table<EFBFBD> 1.33.<2E> Parameters< / b > < / p >
2007-11-06 12:13:52 +00:00
< table class = "table" summary = "Parameters" >
< colgroup >
< col >
< col >
< col >
< / colgroup >
< thead > < tr >
< th >
< p >
Parameter
< / p >
< / th >
< th >
< p >
Requirement
< / p >
< / th >
< th >
< p >
Description
< / p >
< / th >
< / tr > < / thead >
< tbody >
< tr >
< td >
< p >
< tt class = "computeroutput" > < span class = "identifier" > seq< / span > < / tt >
< / p >
< / td >
< td >
< p >
A model of < a href = "../../../sequence/concepts/forward_sequence.html" title = "Forward
Sequence">Forward
Sequence< / a > ,< tt class = "computeroutput" > < span class = "identifier" > f< / span > < span class = "special" > (< / span > < span class = "identifier" > e< / span > < span class = "special" > ,< / span > < span class = "identifier" > s< / span > < span class = "special" > )< / span > < / tt > must be a valid expression for
each element < tt class = "computeroutput" > < span class = "identifier" > e< / span > < / tt >
in < tt class = "computeroutput" > < span class = "identifier" > seq< / span > < / tt > , and current
state < tt class = "computeroutput" > < span class = "identifier" > s< / span > < / tt >
< / p >
< / td >
< td >
< p >
Operation's argument
< / p >
< / td >
< / tr >
< tr >
< td >
< p >
< tt class = "computeroutput" > < span class = "identifier" > initial_state< / span > < / tt >
< / p >
< / td >
< td >
< p >
Any type
< / p >
< / td >
< td >
< p >
Initial state
< / p >
< / td >
< / tr >
< tr >
< td >
< p >
< tt class = "computeroutput" > < span class = "identifier" > f< / span > < / tt >
< / p >
< / td >
< td >
< p >
< tt class = "computeroutput" > < a href = "http://www.boost.org/libs/utility/utility.htm#result_of" target = "_top" > < tt class = "computeroutput" > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > result_of< / span > < / tt > < / a > < span class = "special" > < < / span > < span class = "identifier" > F< / span > < span class = "special" > (< / span > < span class = "identifier" > E< / span > < span class = "special" > ,< / span > < span class = "identifier" > S< / span > < span class = "special" > )> ::< / span > < span class = "identifier" > type< / span > < / tt > is the return type of < tt class = "computeroutput" > < span class = "identifier" > f< / span > < span class = "special" > (< / span > < span class = "identifier" > e< / span > < span class = "special" > ,< / span > < span class = "identifier" > s< / span > < span class = "special" > )< / span > < / tt >
for each element < tt class = "computeroutput" > < span class = "identifier" > e< / span > < / tt >
of type < tt class = "computeroutput" > < span class = "identifier" > E< / span > < / tt > in < tt class = "computeroutput" > < span class = "identifier" > seq< / span > < / tt > , and current state < tt class = "computeroutput" > < span class = "identifier" > s< / span > < / tt > of type < tt class = "computeroutput" > < span class = "identifier" > S< / span > < / tt >
< / p >
< / td >
< td >
< p >
Operation's argument
< / p >
< / td >
< / tr >
< / tbody >
< / table >
< / div >
< a name = "fusion.algorithm.iteration.functions.fold.expression_semantics" > < / a > < h6 >
2007-11-07 03:46:23 +00:00
< a name = "id576277" > < / a >
2007-11-06 12:13:52 +00:00
< a href = "fold.html#fusion.algorithm.iteration.functions.fold.expression_semantics" > Expression
Semantics< / a >
< / h6 >
< pre class = "programlisting" >
< span class = "identifier" > fold< / span > < span class = "special" > (< / span > < span class = "identifier" > seq< / span > < span class = "special" > ,< / span > < span class = "identifier" > initial_state< / span > < span class = "special" > ,< / span > < span class = "identifier" > f< / span > < span class = "special" > );< / span >
< / pre >
< p >
< span class = "bold" > < b > Return type< / b > < / span > : Any type
< / p >
< p >
< span class = "bold" > < b > Semantics< / b > < / span > : Equivalent to < tt class = "computeroutput" > < span class = "identifier" > f< / span > < span class = "special" > (< / span > < span class = "identifier" > eN< / span > < span class = "special" > ....< / span > < span class = "identifier" > f< / span > < span class = "special" > (< / span > < span class = "identifier" > e2< / span > < span class = "special" > ,< / span > < span class = "identifier" > f< / span > < span class = "special" > (< / span > < span class = "identifier" > e1< / span > < span class = "special" > ,< / span > < span class = "identifier" > initial_state< / span > < span class = "special" > )))< / span > < / tt >
where < tt class = "computeroutput" > < span class = "identifier" > e1< / span > < span class = "special" > ...< / span > < span class = "identifier" > eN< / span > < / tt > are the elements of < tt class = "computeroutput" > < span class = "identifier" > seq< / span > < / tt > .
< / p >
< a name = "fusion.algorithm.iteration.functions.fold.complexity" > < / a > < h6 >
2007-11-07 03:46:23 +00:00
< a name = "id576487" > < / a >
2007-11-06 12:13:52 +00:00
< a href = "fold.html#fusion.algorithm.iteration.functions.fold.complexity" > Complexity< / a >
< / h6 >
< p >
Linear, exactly < tt class = "computeroutput" > < a href = "../../../sequence/intrinsic/metafunctions/size.html" title = "size" > < tt class = "computeroutput" > < span class = "identifier" > result_of< / span > < span class = "special" > ::< / span > < span class = "identifier" > size< / span > < / tt > < / a > < span class = "special" > < < / span > < span class = "identifier" > Sequence< / span > < span class = "special" > > ::< / span > < span class = "identifier" > value< / span > < / tt > applications of < tt class = "computeroutput" > < span class = "identifier" > f< / span > < / tt > .
< / p >
< a name = "fusion.algorithm.iteration.functions.fold.header" > < / a > < h6 >
2007-11-07 03:46:23 +00:00
< a name = "id576582" > < / a >
2007-11-06 12:13:52 +00:00
< a href = "fold.html#fusion.algorithm.iteration.functions.fold.header" > Header< / a >
< / h6 >
< pre class = "programlisting" >
< span class = "preprocessor" > #include< / span > < span class = "special" > < < / span > < span class = "identifier" > boost< / span > < span class = "special" > /< / span > < span class = "identifier" > fusion< / span > < span class = "special" > /< / span > < span class = "identifier" > algorithm< / span > < span class = "special" > /< / span > < span class = "identifier" > iteration< / span > < span class = "special" > /< / span > < span class = "identifier" > fold< / span > < span class = "special" > .< / span > < span class = "identifier" > hpp< / span > < span class = "special" > > < / span >
< span class = "preprocessor" > #include< / span > < span class = "special" > < < / span > < span class = "identifier" > boost< / span > < span class = "special" > /< / span > < span class = "identifier" > fusion< / span > < span class = "special" > /< / span > < span class = "identifier" > include< / span > < span class = "special" > /< / span > < span class = "identifier" > fold< / span > < span class = "special" > .< / span > < span class = "identifier" > hpp< / span > < span class = "special" > > < / span >
< / pre >
< a name = "fusion.algorithm.iteration.functions.fold.example" > < / a > < h6 >
2007-11-07 03:46:23 +00:00
< a name = "id576752" > < / a >
2007-11-06 12:13:52 +00:00
< a href = "fold.html#fusion.algorithm.iteration.functions.fold.example" > Example< / a >
< / h6 >
< pre class = "programlisting" >
< span class = "keyword" > struct< / span > < span class = "identifier" > make_string< / span >
< span class = "special" > {< / span >
< span class = "keyword" > typedef< / span > < span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > string< / span > < span class = "identifier" > result_type< / span > < span class = "special" > ;< / span >
< span class = "keyword" > template< / span > < span class = "special" > < < / span > < span class = "keyword" > typename< / span > < span class = "identifier" > T< / span > < span class = "special" > > < / span >
< span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > string< / span > < span class = "keyword" > operator< / span > < span class = "special" > ()(< / span > < span class = "keyword" > const< / span > < span class = "identifier" > T< / span > < span class = "special" > & < / span > < span class = "identifier" > t< / span > < span class = "special" > ,< / span > < span class = "keyword" > const< / span > < span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > string< / span > < span class = "special" > & < / span > < span class = "identifier" > str< / span > < span class = "special" > )< / span > < span class = "keyword" > const< / span >
< span class = "special" > {< / span >
< span class = "keyword" > return< / span > < span class = "identifier" > str< / span > < span class = "special" > +< / span > < span class = "identifier" > boost< / span > < span class = "special" > ::< / span > < span class = "identifier" > lexical_cast< / span > < span class = "special" > < < / span > < span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > string< / span > < span class = "special" > > (< / span > < span class = "identifier" > t< / span > < span class = "special" > );< / span >
< span class = "special" > }< / span >
< span class = "special" > };< / span >
< span class = "special" > ...< / span >
< span class = "keyword" > const< / span > < a href = "../../../container/vector.html" title = "vector" > < tt class = "computeroutput" > < span class = "identifier" > vector< / span > < / tt > < / a > < span class = "special" > < < / span > < span class = "keyword" > int< / span > < span class = "special" > ,< / span > < span class = "keyword" > int< / span > < span class = "special" > > < / span > < span class = "identifier" > vec< / span > < span class = "special" > (< / span > < span class = "number" > 1< / span > < span class = "special" > ,< / span > < span class = "number" > 2< / span > < span class = "special" > );< / span >
< span class = "identifier" > assert< / span > < span class = "special" > (< / span > < a href = "fold.html" title = "fold" > < tt class = "computeroutput" > < span class = "identifier" > fold< / span > < / tt > < / a > < span class = "special" > (< / span > < span class = "identifier" > vec< / span > < span class = "special" > ,< / span > < span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > string< / span > < span class = "special" > (< / span > < span class = "string" > ""< / span > < span class = "special" > ),< / span > < span class = "identifier" > make_string< / span > < span class = "special" > ())< / span > < span class = "special" > ==< / span > < span class = "string" > "12"< / span > < span class = "special" > );< / span >
< / pre >
< / div >
< table xmlns:rev = "http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width = "100%" > < tr >
< td align = "left" > < / td >
2007-11-07 02:12:28 +00:00
< td align = "right" > < div class = "copyright-footer" > < small > Copyright <20> 2001-2007 Joel de Guzman, Dan Marsden, Tobias
Schwinger< p >
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at < a href = "http://www.boost.org/LICENSE_1_0.txt" target = "_top" > http://www.boost.org/LICENSE_1_0.txt< / a > )
< / p > < / small > < / div > < / td >
2007-11-06 12:13:52 +00:00
< / tr > < / table >
< hr >
< div class = "spirit-nav" >
< a accesskey = "p" href = "../functions.html" > < img src = "../../../../../../../../doc/html/images/prev.png" alt = "Prev" > < / a > < a accesskey = "u" href = "../functions.html" > < img src = "../../../../../../../../doc/html/images/up.png" alt = "Up" > < / a > < a accesskey = "h" href = "../../../../index.html" > < img src = "../../../../../../../../doc/html/images/home.png" alt = "Home" > < / a > < a accesskey = "n" href = "accumulate.html" > < img src = "../../../../../../../../doc/html/images/next.png" alt = "Next" > < / a >
< / div >
< / body >
< / html >
