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< title > cons</ title >
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< div class = "titlepage" >< div >< div >< h4 class = "title" >
< a name = "fusion.sequences.containers.cons" ></ a >< a href = "cons.html" title = "cons" > cons</ a ></ h4 ></ div ></ div ></ div >
< a name = "fusion.sequences.containers.cons.description" ></ a >< h5 >
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< a name = "id484257" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.description" > Description</ a >
</ h5 >
< p >
< tt class = "computeroutput" >< span class = "identifier" > cons</ span ></ tt > is a simple < a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward Sequence</ a > .
It is a lisp style recursive list structure where < tt class = "computeroutput" >< span class = "identifier" > car</ span ></ tt >
is the < span class = "emphasis" >< em > head</ em ></ span > and < tt class = "computeroutput" >< span class = "identifier" > cdr</ span ></ tt >
is the < span class = "emphasis" >< em > tail</ em ></ span > : usually another cons structure or < tt class = "computeroutput" >< span class = "identifier" > nil</ span ></ tt > : the empty list. Fusion's < a href = "list.html" title = "list" >< tt class = "computeroutput" >< span class = "identifier" > list</ span ></ tt ></ a > is built on top of this more
primitive data structure. It is more efficient than < a href = "vector.html" title = "vector" >< tt class = "computeroutput" >< span class = "identifier" > vector</ span ></ tt ></ a > when the target sequence
is constructed piecemeal (a data at a time). The runtime cost of access
to each element is peculiarly constant (see < a href = "../../notes.html#fusion.notes.recursive_inlined_functions" > Recursive
Inlined Functions</ a > ).
</ p >
< a name = "fusion.sequences.containers.cons.header" ></ a >< h5 >
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< a name = "id484394" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.header" > Header</ a >
</ h5 >
< 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" > sequence</ span >< span class = "special" > /</ span >< span class = "identifier" > container</ span >< span class = "special" > /</ span >< span class = "identifier" > list</ span >< span class = "special" > /</ span >< span class = "identifier" > cons</ span >< span class = "special" > .</ span >< span class = "identifier" > hpp</ span >< span class = "special" > > </ span >
</ pre >
< a name = "fusion.sequences.containers.cons.synopsis" ></ a >< h5 >
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< a name = "id484508" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.synopsis" > Synopsis</ a >
</ h5 >
< pre class = "programlisting" >
< span class = "keyword" > template</ span > < span class = "special" > < </ span >< span class = "keyword" > typename</ span > < span class = "identifier" > Car</ span >< span class = "special" > ,</ span > < span class = "keyword" > typename</ span > < span class = "identifier" > Cdr</ span > < span class = "special" > =</ span > < span class = "identifier" > nil</ span >< span class = "special" > > </ span >
< span class = "keyword" > struct</ span > < span class = "identifier" > cons</ span >< span class = "special" > ;</ span >
</ pre >
< a name = "fusion.sequences.containers.cons.template_parameters" ></ a >< h5 >
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< a name = "id484616" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.template_parameters" > Template
parameters</ a >
</ h5 >
< div class = "informaltable" >
< h4 >
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< a name = "id484638" ></ a >
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</ h4 >
< table class = "table" >
< colgroup >
< col >
< col >
< col >
</ colgroup >
< thead >< tr >
< th > Parameter</ th >
< th > Description</ th >
< th > Default</ th >
</ tr ></ thead >
< tbody >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > Car</ span ></ tt ></ td >
< td > Head
type</ td >
< td > </ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > Cdr</ span ></ tt ></ td >
< td > Tail
type</ td >
< td >< tt class = "computeroutput" >< span class = "identifier" > nil</ span ></ tt ></ td >
</ tr >
</ tbody >
</ table >
</ div >
< a name = "fusion.sequences.containers.cons.model_of" ></ a >< h5 >
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< a name = "id484727" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.model_of" > Model of</ a >
</ h5 >
< div class = "itemizedlist" >< ul type = "disc" >< li >< a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward Sequence</ a ></ li ></ ul ></ div >
< div class = "variablelist" >
< p class = "title" >< b > Notation</ b ></ p >
< dl >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > nil</ span ></ tt ></ span ></ dt >
< dd >
An empty < tt class = "computeroutput" >< span class = "identifier" > cons</ span ></ tt >
</ dd >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > C</ span ></ tt ></ span ></ dt >
< dd >
A < tt class = "computeroutput" >< span class = "identifier" > cons</ span ></ tt > type
</ dd >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > l</ span ></ tt > ,
< tt class = "computeroutput" >< span class = "identifier" > l2</ span ></ tt ></ span ></ dt >
< dd >
Instances of < tt class = "computeroutput" >< span class = "identifier" > cons</ span ></ tt >
</ dd >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > car</ span ></ tt ></ span ></ dt >
< dd >
An arbitrary data
</ dd >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > cdr</ span ></ tt ></ span ></ dt >
< dd >
Another < tt class = "computeroutput" >< span class = "identifier" > cons</ span ></ tt > list
</ dd >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > s</ span ></ tt ></ span ></ dt >
< dd >
A < a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward
Sequence</ a >
</ dd >
< dt >< span class = "term" >< tt class = "computeroutput" >< span class = "identifier" > N</ span ></ tt ></ span ></ dt >
< dd >
An Integral Constant
</ dd >
</ dl >
</ div >
< a name = "fusion.sequences.containers.cons.expression_semantics" ></ a >< h5 >
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< a name = "id484959" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.expression_semantics" > Expression
Semantics</ a >
</ h5 >
< p >
Semantics of an expression is defined only where it differs from, or is
not defined in < a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward
Sequence</ a > .
</ p >
< div class = "informaltable" >
< h4 >
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< a name = "id484996" ></ a >
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</ h4 >
< table class = "table" >
< colgroup >
< col >
< col >
</ colgroup >
< thead >< tr >
< th > Expression</ th >
< th > Semantics</ th >
</ tr ></ thead >
< tbody >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > nil</ span >< span class = "special" > ()</ span ></ tt ></ td >
< td > Creates
an empty list.</ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > C</ span >< span class = "special" > ()</ span ></ tt ></ td >
< td > Creates
a cons with default constructed elements.</ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > C</ span >< span class = "special" > (</ span >< span class = "identifier" > car</ span >< span class = "special" > )</ span ></ tt ></ td >
< td > Creates
a cons with < tt class = "computeroutput" >< span class = "identifier" > car</ span ></ tt > head
and default constructed tail.</ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > C</ span >< span class = "special" > (</ span >< span class = "identifier" > car</ span >< span class = "special" > ,</ span > < span class = "identifier" > cdr</ span >< span class = "special" > )</ span ></ tt ></ td >
< td > Creates
a cons with < tt class = "computeroutput" >< span class = "identifier" > car</ span ></ tt > head
and < tt class = "computeroutput" >< span class = "identifier" > cdr</ span ></ tt > tail.</ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > C</ span >< span class = "special" > (</ span >< span class = "identifier" > s</ span >< span class = "special" > )</ span ></ tt ></ td >
< td > Copy
constructs a cons from a < a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward
Sequence</ a > , < tt class = "computeroutput" >< span class = "identifier" > s</ span ></ tt > .</ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > l</ span > < span class = "special" > =</ span > < span class = "identifier" > s</ span ></ tt ></ td >
< td > Assigns to a cons,
< tt class = "computeroutput" >< span class = "identifier" > l</ span ></ tt > , from a < a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward
Sequence</ a > , < tt class = "computeroutput" >< span class = "identifier" > s</ span ></ tt > .</ td >
</ tr >
< tr >
< td >< tt class = "computeroutput" >< a href = "../intrinsics/functions/at.html" title = "at" >< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt ></ a >< span class = "special" > < </ span >< span class = "identifier" > N</ span >< span class = "special" > > (</ span >< span class = "identifier" > l</ span >< span class = "special" > )</ span ></ tt ></ td >
< td > The
Nth element from the beginning of the sequence; see < a href = "../intrinsics/functions/at.html" title = "at" >< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt ></ a > .</ td >
</ tr >
</ tbody >
</ table >
</ div >
< p class = "blurb" >
< span class = "inlinemediaobject" >< img src = "../../../images/note.png" alt = "note" ></ span > < tt class = "computeroutput" >< a href = "../intrinsics/functions/at.html" title = "at" >< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt ></ a >< span class = "special" > < </ span >< span class = "identifier" > N</ span >< span class = "special" > > (</ span >< span class = "identifier" > l</ span >< span class = "special" > )</ span ></ tt > is
provided for convenience and compatibility with the original < a href = "http://www.boost.org/libs/tuple/doc/tuple_users_guide.html" target = "_top" > Boost.Tuple</ a >
library, despite < tt class = "computeroutput" >< span class = "identifier" > cons</ span ></ tt > being
a < a href = "../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward Sequence</ a >
only (< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt > is supposed to
be a < a href = "../concepts/random_access_sequence.html" title = "Random
Access Sequence" > Random
Access Sequence</ a > requirement). The runtime complexity of < a href = "../intrinsics/functions/at.html" title = "at" >< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt ></ a > is constant (see < a href = "../../notes.html#fusion.notes.recursive_inlined_functions" > Recursive
Inlined Functions</ a > ).
</ p >
< a name = "fusion.sequences.containers.cons.example" ></ a >< h5 >
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< a name = "id485510" ></ a >
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< a href = "cons.html#fusion.sequences.containers.cons.example" > Example</ a >
</ h5 >
< pre class = "programlisting" >
< span class = "identifier" > cons</ span >< span class = "special" > < </ span >< span class = "keyword" > int</ span >< span class = "special" > ,</ span > < span class = "identifier" > cons</ span >< span class = "special" > < </ span >< span class = "keyword" > float</ span >< span class = "special" > > </ span > < span class = "special" > > </ span > < span class = "identifier" > l</ span >< span class = "special" > (</ span >< span class = "number" > 12</ span >< span class = "special" > ,</ span > < span class = "identifier" > cons</ span >< span class = "special" > < </ span >< span class = "keyword" > float</ span >< span class = "special" > > (</ span >< span class = "number" > 5.5f</ span >< span class = "special" > ));</ span >
< span class = "identifier" > std</ span >< span class = "special" > ::</ span >< span class = "identifier" > cout</ span > < span class = "special" > << </ span > < a href = "../intrinsics/functions/at.html" title = "at" >< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt ></ a >< span class = "special" > < </ span >< span class = "number" > 0</ span >< span class = "special" > > (</ span >< span class = "identifier" > l</ span >< span class = "special" > )</ span > < span class = "special" > << </ span > < span class = "identifier" > std</ span >< span class = "special" > ::</ span >< span class = "identifier" > endl</ span >< span class = "special" > ;</ span >
< span class = "identifier" > std</ span >< span class = "special" > ::</ span >< span class = "identifier" > cout</ span > < span class = "special" > << </ span > < a href = "../intrinsics/functions/at.html" title = "at" >< tt class = "computeroutput" >< span class = "identifier" > at</ span ></ tt ></ a >< span class = "special" > < </ span >< span class = "number" > 1</ span >< span class = "special" > > (</ span >< span class = "identifier" > l</ span >< span class = "special" > )</ span > < span class = "special" > << </ span > < span class = "identifier" > std</ span >< span class = "special" > ::</ span >< span class = "identifier" > endl</ span >< span class = "special" > ;</ span >
</ pre >
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< td align = "right" >< small > Copyright © 2001-2005 Joel de Guzman, Dan Marsden</ small ></ td >
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