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< a name = "fusion.sequences.intrinsics.functions.front" ></ a >< a href = "front.html" title = "front" > front</ a ></ h5 ></ div ></ div ></ div >
< a name = "fusion.sequences.intrinsics.functions.front.description" ></ a >< h6 >
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< a name = "id504838" ></ a >
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< a href = "front.html#fusion.sequences.intrinsics.functions.front.description" > Description</ a >
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< p >
Returns the first element in the sequence.
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< a name = "fusion.sequences.intrinsics.functions.front.synopsis" ></ a >< h6 >
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< a name = "id504868" ></ a >
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< a href = "front.html#fusion.sequences.intrinsics.functions.front.synopsis" > Synopsis</ a >
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< 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 > < a href = "../metafunctions/front.html" title = "front" >< tt class = "computeroutput" >< span class = "identifier" > result_of</ span >< span class = "special" > ::</ span >< span class = "identifier" > front</ span ></ tt ></ a >< span class = "special" > < </ span >< span class = "identifier" > Sequence</ span >< span class = "special" > > ::</ span >< span class = "identifier" > type</ span >
< span class = "identifier" > front</ 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 = "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 > < a href = "../metafunctions/front.html" title = "front" >< tt class = "computeroutput" >< span class = "identifier" > result_of</ span >< span class = "special" > ::</ span >< span class = "identifier" > front</ span ></ tt ></ a >< span class = "special" > < </ span >< span class = "identifier" > Sequence</ span > < span class = "keyword" > const</ span >< span class = "special" > > ::</ span >< span class = "identifier" > type</ span >
< span class = "identifier" > front</ span >< span class = "special" > (</ span >< span class = "identifier" > Sequence</ span > < span class = "keyword" > const</ span >< span class = "special" > & </ span > < span class = "identifier" > seq</ span >< span class = "special" > );</ span >
</ pre >
< a name = "fusion.sequences.intrinsics.functions.front.parameters" ></ a >< h6 >
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< a name = "id505144" ></ a >
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< a href = "front.html#fusion.sequences.intrinsics.functions.front.parameters" > Parameters</ a >
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< div class = "informaltable" >
< h4 >
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< a name = "id505166" ></ a >
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</ h4 >
< table class = "table" >
< colgroup >
< col >
< col >
< col >
</ colgroup >
< thead >< tr >
< th > Parameter</ th >
< th > Requirement</ th >
< th > Description</ th >
</ tr ></ thead >
< tbody >< tr >
< td >< tt class = "computeroutput" >< span class = "identifier" > seq</ span ></ tt ></ td >
< td > Model
of < a href = "../../concepts/forward_sequence.html" title = "Forward
Sequence" > Forward
Sequence</ a >
</ td >
< td > The sequence we wish to investigate.</ td >
</ tr ></ tbody >
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< a name = "fusion.sequences.intrinsics.functions.front.expression_semantics" ></ a >< h6 >
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< a name = "id505238" ></ a >
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< a href = "front.html#fusion.sequences.intrinsics.functions.front.expression_semantics" > Expression
Semantics</ a >
</ h6 >
< pre class = "programlisting" >
< span class = "identifier" > front</ span >< span class = "special" > (</ span >< span class = "identifier" > seq</ span >< span class = "special" > );</ span >
</ pre >
< p >
< span class = "bold" >< b > Return type</ b ></ span > : Returns a reference to
the first element in the sequence < tt class = "computeroutput" >< span class = "identifier" > seq</ span ></ tt >
if < tt class = "computeroutput" >< span class = "identifier" > seq</ span ></ tt > is mutable and
< tt class = "computeroutput" >< span class = "identifier" > e</ span > < span class = "special" > =</ span > < span class = "identifier" > o</ span ></ tt > , where < tt class = "computeroutput" >< span class = "identifier" > e</ span ></ tt >
is the first element in the sequence, is a valid expression. Else, returns
a type convertable to the first element in the sequence.
</ p >
< p >
< span class = "bold" >< b > Precondition</ b ></ span > : < tt class = "computeroutput" >< a href = "empty.html" title = "empty" >< tt class = "computeroutput" >< span class = "identifier" > empty</ span ></ tt ></ a >< span class = "special" > (</ span >< span class = "identifier" > seq</ span >< span class = "special" > )</ span > < span class = "special" > ==</ span > < span class = "keyword" > false</ span ></ tt >
</ p >
< p >
< span class = "bold" >< b > Semantics</ b ></ span > : Returns the first element
in the sequence.
</ p >
< a name = "fusion.sequences.intrinsics.functions.front.header" ></ a >< h6 >
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< a name = "id505428" ></ a >
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< a href = "front.html#fusion.sequences.intrinsics.functions.front.header" > Header</ a >
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< 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" > intrinsic</ span >< span class = "special" > /</ span >< span class = "identifier" > front</ span >< span class = "special" > .</ span >< span class = "identifier" > hpp</ span >< span class = "special" > > </ span >
</ pre >
< a name = "fusion.sequences.intrinsics.functions.front.example" ></ a >< h6 >
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< a name = "id505533" ></ a >
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< a href = "front.html#fusion.sequences.intrinsics.functions.front.example" > Example</ a >
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< a href = "../../containers/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 = "keyword" > int</ span >< span class = "special" > > </ span > < span class = "identifier" > v</ 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 = "number" > 3</ span >< span class = "special" > );</ span >
< span class = "identifier" > assert</ span >< span class = "special" > (</ span >< span class = "identifier" > front</ span >< span class = "special" > (</ span >< span class = "identifier" > v</ span >< span class = "special" > )</ span > < span class = "special" > ==</ span > < span class = "number" > 1</ span >< span class = "special" > );</ span >
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< td align = "right" >< small > Copyright © 2001-2005 Joel de Guzman, Dan Marsden</ small ></ td >
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