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< title > Function Output Iterator< / title >
< meta name = "author" content = "David Abrahams, Jeremy Siek, Thomas Witt" / >
< meta name = "organization" content = "Boost Consulting, Indiana University Open Systems Lab, University of Hanover Institute for Transport Railway Operation and Construction" / >
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< meta name = "date" content = "2004-01-12" / >
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< div class = "document" id = "function-output-iterator" >
< h1 class = "title" > Function Output Iterator< / h1 >
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< tr > < th class = "docinfo-name" > Author:< / th >
< td > David Abrahams, Jeremy Siek, Thomas Witt< / td > < / tr >
< tr > < th class = "docinfo-name" > Contact:< / th >
< td > < a class = "first reference" href = "mailto:dave@boost-consulting.com" > dave@ boost-consulting.com< / a > , < a class = "reference" href = "mailto:jsiek@osl.iu.edu" > jsiek@ osl.iu.edu< / a > , < a class = "last reference" href = "mailto:witt@ive.uni-hannover.de" > witt@ ive.uni-hannover.de< / a > < / td > < / tr >
< tr > < th class = "docinfo-name" > Organization:< / th >
< td > < a class = "first reference" href = "http://www.boost-consulting.com" > Boost Consulting< / a > , Indiana University < a class = "reference" href = "http://www.osl.iu.edu" > Open Systems
Lab< / a > , University of Hanover < a class = "last reference" href = "http://www.ive.uni-hannover.de" > Institute for Transport
Railway Operation and Construction< / a > < / td > < / tr >
< tr > < th class = "docinfo-name" > Date:< / th >
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< td > 2004-01-12< / td > < / tr >
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< tr > < th class = "docinfo-name" > Copyright:< / th >
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< td > Copyright David Abrahams, Jeremy Siek, and Thomas Witt 2003. All rights reserved< / td > < / tr >
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< tr class = "field" > < th class = "field-name" > abstract:< / th > < td class = "field-body" > < / td >
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< p > The function output iterator adaptor makes it easier to create custom
output iterators. The adaptor takes a unary function and creates a
model of Output Iterator. Each item assigned to the output iterator is
passed as an argument to the unary function. The motivation for this
iterator is that creating a conforming output iterator is non-trivial,
particularly because the proper implementation usually requires a
proxy object.< / p >
< div class = "contents topic" id = "table-of-contents" >
< p class = "topic-title" > < a name = "table-of-contents" > Table of Contents< / a > < / p >
< ul class = "simple" >
< li > < a class = "reference" href = "#function-output-iterator-requirements" id = "id1" name = "id1" > < tt class = "literal" > < span class = "pre" > function_output_iterator< / span > < / tt > requirements< / a > < / li >
< li > < a class = "reference" href = "#function-output-iterator-operations" id = "id2" name = "id2" > < tt class = "literal" > < span class = "pre" > function_output_iterator< / span > < / tt > operations< / a > < / li >
< li > < a class = "reference" href = "#function-output-iterator-output-proxy-operations" id = "id3" name = "id3" > < tt class = "literal" > < span class = "pre" > function_output_iterator::output_proxy< / span > < / tt > operations< / a > < / li >
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< li > < a class = "reference" href = "#example" id = "id4" name = "id4" > Example< / a > < / li >
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< / ul >
< / div >
< pre class = "literal-block" >
template < class UnaryFunction>
class function_output_iterator {
public:
typedef iterator_tag<
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writable_iterator
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, incrementable_traversal_tag
> iterator_category;
typedef void value_type;
typedef void difference_type;
typedef void pointer;
typedef void reference;
explicit function_output_iterator(const UnaryFunction& f = UnaryFunction());
struct output_proxy {
output_proxy(UnaryFunction& f);
template < class T> output_proxy& operator=(const T& value);
};
output_proxy operator*();
function_output_iterator& operator++();
function_output_iterator& operator++(int);
};
< / pre >
< div class = "section" id = "function-output-iterator-requirements" >
< h1 > < a class = "toc-backref" href = "#id1" name = "function-output-iterator-requirements" > < tt class = "literal" > < span class = "pre" > function_output_iterator< / span > < / tt > requirements< / a > < / h1 >
< p > The < tt class = "literal" > < span class = "pre" > UnaryFunction< / span > < / tt > must be Assignable, Copy Constructible, and the
expression < tt class = "literal" > < span class = "pre" > f(x)< / span > < / tt > must be valid, where < tt class = "literal" > < span class = "pre" > f< / span > < / tt > is an object of type
< tt class = "literal" > < span class = "pre" > UnaryFunction< / span > < / tt > and < tt class = "literal" > < span class = "pre" > x< / span > < / tt > is an object of a type accepted by < tt class = "literal" > < span class = "pre" > f< / span > < / tt > .
The resulting < tt class = "literal" > < span class = "pre" > function_output_iterator< / span > < / tt > is a model of the Writable
and Incrementable Iterator concepts.< / p >
< / div >
< div class = "section" id = "function-output-iterator-operations" >
< h1 > < a class = "toc-backref" href = "#id2" name = "function-output-iterator-operations" > < tt class = "literal" > < span class = "pre" > function_output_iterator< / span > < / tt > operations< / a > < / h1 >
< p > < tt class = "literal" > < span class = "pre" > explicit< / span > < span class = "pre" > function_output_iterator(const< / span > < span class = "pre" > UnaryFunction& < / span > < span class = "pre" > f< / span > < span class = "pre" > =< / span > < span class = "pre" > UnaryFunction());< / span > < / tt > < / p >
< table class = "field-list" frame = "void" rules = "none" >
< col class = "field-name" / >
< col class = "field-body" / >
< tbody valign = "top" >
< tr class = "field" > < th class = "field-name" > Returns:< / th > < td class = "field-body" > An instance of < tt class = "literal" > < span class = "pre" > function_output_iterator< / span > < / tt > with
< tt class = "literal" > < span class = "pre" > f< / span > < / tt > stored as a data member.< / td >
< / tr >
< / tbody >
< / table >
< p > < tt class = "literal" > < span class = "pre" > output_proxy< / span > < span class = "pre" > operator*();< / span > < / tt > < / p >
< table class = "field-list" frame = "void" rules = "none" >
< col class = "field-name" / >
< col class = "field-body" / >
< tbody valign = "top" >
< tr class = "field" > < th class = "field-name" > Returns:< / th > < td class = "field-body" > An instance of < tt class = "literal" > < span class = "pre" > output_proxy< / span > < / tt > constructed with
a copy of the unary function < tt class = "literal" > < span class = "pre" > f< / span > < / tt > .< / td >
< / tr >
< / tbody >
< / table >
< p > < tt class = "literal" > < span class = "pre" > function_output_iterator& < / span > < span class = "pre" > operator++();< / span > < / tt > < / p >
< table class = "field-list" frame = "void" rules = "none" >
< col class = "field-name" / >
< col class = "field-body" / >
< tbody valign = "top" >
< tr class = "field" > < th class = "field-name" > Returns:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > *this< / span > < / tt > < / td >
< / tr >
< / tbody >
< / table >
< p > < tt class = "literal" > < span class = "pre" > function_output_iterator& < / span > < span class = "pre" > operator++(int);< / span > < / tt > < / p >
< table class = "field-list" frame = "void" rules = "none" >
< col class = "field-name" / >
< col class = "field-body" / >
< tbody valign = "top" >
< tr class = "field" > < th class = "field-name" > Returns:< / th > < td class = "field-body" > < tt class = "literal" > < span class = "pre" > *this< / span > < / tt > < / td >
< / tr >
< / tbody >
< / table >
< / div >
< div class = "section" id = "function-output-iterator-output-proxy-operations" >
< h1 > < a class = "toc-backref" href = "#id3" name = "function-output-iterator-output-proxy-operations" > < tt class = "literal" > < span class = "pre" > function_output_iterator::output_proxy< / span > < / tt > operations< / a > < / h1 >
< p > < tt class = "literal" > < span class = "pre" > output_proxy(UnaryFunction& < / span > < span class = "pre" > f);< / span > < / tt > < / p >
< table class = "field-list" frame = "void" rules = "none" >
< col class = "field-name" / >
< col class = "field-body" / >
< tbody valign = "top" >
< tr class = "field" > < th class = "field-name" > Returns:< / th > < td class = "field-body" > An instance of < tt class = "literal" > < span class = "pre" > output_proxy< / span > < / tt > with < tt class = "literal" > < span class = "pre" > f< / span > < / tt > stored as
a data member.< / td >
< / tr >
< / tbody >
< / table >
< p > < tt class = "literal" > < span class = "pre" > template< / span > < span class = "pre" > < class< / span > < span class = "pre" > T> < / span > < span class = "pre" > output_proxy& < / span > < span class = "pre" > operator=(const< / span > < span class = "pre" > T& < / span > < span class = "pre" > value);< / span > < / tt > < / p >
< table class = "field-list" frame = "void" rules = "none" >
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< tr class = "field" > < th class = "field-name" > Effects:< / th > < td class = "field-body" > < pre class = "first last literal-block" >
m_f(value);
return *this;
< / pre >
< / td >
< / tr >
< / tbody >
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< div class = "section" id = "example" >
< h1 > < a class = "toc-backref" href = "#id4" name = "example" > Example< / a > < / h1 >
< pre class = "literal-block" >
struct string_appender
{
string_appender(std::string& s)
: m_str(& s)
{}
void operator()(const std::string& x) const
{
*m_str += x;
}
std::string* m_str;
};
int main(int, char*[])
{
std::vector< std::string> x;
x.push_back(" hello" );
x.push_back(" " );
x.push_back(" world" );
x.push_back(" !" );
std::string s = " " ;
std::copy(x.begin(), x.end(),
boost::make_function_output_iterator(string_appender(s)));
std::cout < < s < < std::endl;
return 0;
}
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