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< a name = "fusion.container.generation.functions.tiers" > < / a > < a class = "link" href = "tiers.html" title = "Tiers" > Tiers< / a >
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< p >
Tiers are sequences, where all elements are non-const reference types.
They are constructed with a call to a couple of < span class = "emphasis" > < em > tie< / em > < / span >
function templates. The succeeding sections document the various < span class = "emphasis" > < em > tier< / em > < / span >
flavors.
< / p >
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< div class = "itemizedlist" > < ul class = "itemizedlist" type = "disc" >
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< li class = "listitem" > < a class = "link" href = "list_tie.html" title = "list_tie" > < code class = "computeroutput" > < span class = "identifier" > list_tie< / span > < / code > < / a > < / li >
< li class = "listitem" > < a class = "link" href = "vector_tie.html" title = "vector_tie" > < code class = "computeroutput" > < span class = "identifier" > vector_tie< / span > < / code > < / a > < / li >
< li class = "listitem" > < a class = "link" href = "vector_tie.html" title = "vector_tie" > < code class = "computeroutput" > < span class = "identifier" > map_tie< / span > < / code > < / a > < / li >
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< / ul > < / div >
< p >
Example:
< / p >
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< pre class = "programlisting" > < span class = "keyword" > int< / span > < span class = "identifier" > i< / span > < span class = "special" > ;< / span > < span class = "keyword" > char< / span > < span class = "identifier" > c< / span > < span class = "special" > ;< / span > < span class = "keyword" > double< / span > < span class = "identifier" > d< / span > < span class = "special" > ;< / span >
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< span class = "special" > ...< / span >
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< a class = "link" href = "vector_tie.html" title = "vector_tie" > < code class = "computeroutput" > < span class = "identifier" > vector_tie< / span > < / code > < / a > < span class = "special" > (< / span > < span class = "identifier" > i< / span > < span class = "special" > ,< / span > < span class = "identifier" > c< / span > < span class = "special" > ,< / span > < span class = "identifier" > a< / span > < span class = "special" > );< / span >
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< / pre >
< p >
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The < a class = "link" href = "vector_tie.html" title = "vector_tie" > < code class = "computeroutput" > < span class = "identifier" > vector_tie< / span > < / code > < / a > function creates
a < a class = "link" href = "../../vector.html" title = "vector" > < code class = "computeroutput" > < span class = "identifier" > vector< / span > < / code > < / a >
of type < code class = "computeroutput" > < a class = "link" href = "../../vector.html" title = "vector" > < code class = "computeroutput" > < span class = "identifier" > vector< / span > < / code > < / a > < span class = "special" > < < / span > < span class = "keyword" > int< / span > < span class = "special" > & ,< / span > < span class = "keyword" > char< / span > < span class = "special" > & ,< / span > < span class = "keyword" > double< / span > < span class = "special" > & > < / span > < / code > . The same result could be achieved
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with the call < a class = "link" href = "make_vector.html" title = "make_vector" > < code class = "computeroutput" > < span class = "identifier" > make_vector< / span > < / code > < / a > (< a href = "http://www.boost.org/doc/html/ref.html" target = "_top" > < code class = "computeroutput" > < span class = "identifier" > ref< / span > < / code > < / a > (i), < a href = "http://www.boost.org/doc/html/ref.html" target = "_top" > < code class = "computeroutput" > < span class = "identifier" > ref< / span > < / code > < / a > (c), < a href = "http://www.boost.org/doc/html/ref.html" target = "_top" > < code class = "computeroutput" > < span class = "identifier" > ref< / span > < / code > < / a > (a))
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< sup > [< a name = "id955322" href = "#ftn.id955322" class = "footnote" > 9< / a > ]< / sup >
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.
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< / p >
< p >
A < span class = "emphasis" > < em > tie< / em > < / span > can be used to 'unpack' another tuple into
variables. E.g.:
< / p >
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< pre class = "programlisting" > < span class = "keyword" > int< / span > < span class = "identifier" > i< / span > < span class = "special" > ;< / span > < span class = "keyword" > char< / span > < span class = "identifier" > c< / span > < span class = "special" > ;< / span > < span class = "keyword" > double< / span > < span class = "identifier" > d< / span > < span class = "special" > ;< / span >
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< a class = "link" href = "vector_tie.html" title = "vector_tie" > < code class = "computeroutput" > < span class = "identifier" > vector_tie< / span > < / code > < / a > < span class = "special" > (< / span > < span class = "identifier" > i< / span > < span class = "special" > ,< / span > < span class = "identifier" > c< / span > < span class = "special" > ,< / span > < span class = "identifier" > d< / span > < span class = "special" > )< / span > < span class = "special" > =< / span > < a class = "link" href = "make_vector.html" title = "make_vector" > < code class = "computeroutput" > < span class = "identifier" > make_vector< / span > < / code > < / a > < span class = "special" > (< / span > < span class = "number" > 1< / span > < span class = "special" > ,< / span > < span class = "char" > 'a'< / span > < span class = "special" > ,< / span > < span class = "number" > 5.5< / span > < span class = "special" > );< / span >
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< span class = "identifier" > std< / span > < span class = "special" > ::< / span > < span class = "identifier" > cout< / span > < span class = "special" > < < < / span > < span class = "identifier" > i< / span > < span class = "special" > < < < / span > < span class = "string" > " "< / span > < span class = "special" > < < < / span > < span class = "identifier" > c< / span > < span class = "special" > < < < / span > < span class = "string" > " "< / span > < span class = "special" > < < < / span > < span class = "identifier" > d< / span > < span class = "special" > ;< / span >
< / pre >
< p >
This code prints 1 a 5.5 to the standard output stream. A sequence unpacking
operation like this is found for example in ML and Python. It is convenient
when calling functions which return sequences.
< / p >
< a name = "fusion.container.generation.functions.tiers.ignore" > < / a > < h6 >
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< a name = "id955542" > < / a >
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< a class = "link" href = "tiers.html#fusion.container.generation.functions.tiers.ignore" > Ignore< / a >
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< / h6 >
< p >
There is also an object called < span class = "emphasis" > < em > ignore< / em > < / span > which allows
you to ignore an element assigned by a sequence. The idea is that a function
may return a sequence, only part of which you are interested in. For
example:
< / p >
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< pre class = "programlisting" > < span class = "keyword" > char< / span > < span class = "identifier" > c< / span > < span class = "special" > ;< / span >
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< a class = "link" href = "vector_tie.html" title = "vector_tie" > < code class = "computeroutput" > < span class = "identifier" > vector_tie< / span > < / code > < / a > < span class = "special" > (< / span > < span class = "identifier" > ignore< / span > < span class = "special" > ,< / span > < span class = "identifier" > c< / span > < span class = "special" > )< / span > < span class = "special" > =< / span > < a class = "link" href = "make_vector.html" title = "make_vector" > < code class = "computeroutput" > < span class = "identifier" > make_vector< / span > < / code > < / a > < span class = "special" > (< / span > < span class = "number" > 1< / span > < span class = "special" > ,< / span > < span class = "char" > 'a'< / span > < span class = "special" > );< / span >
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< / pre >
< div class = "footnotes" >
< br > < hr width = "100" align = "left" >
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< div class = "footnote" > < p > < sup > [< a name = "ftn.id955322" href = "#id955322" class = "para" > 9< / a > ] < / sup >
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see < a href = "http://www.boost.org/doc/html/ref.html" target = "_top" > Boost.Ref< / a >
for details about < code class = "computeroutput" > < span class = "identifier" > ref< / span > < / code >
< / p > < / div >
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< td align = "right" > < div class = "copyright-footer" > Copyright © 2001-2007 Joel de Guzman, Dan Marsden, Tobias
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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 > )
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