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It is provided "as is" without express or implied warranty. -- --><Head><Title>mem_fun1_t<Result, X, Arg></Title><!-- Generated by htmldoc --></HEAD><BODY TEXT="#000000" LINK="#006600" ALINK="#003300" VLINK="#7C7F87" BGCOLOR="#FFFFFF"><A HREF="/"><IMG SRC="/images/common/sgilogo_small.gif" ALT="SGI Logo" WIDTH="80" HEIGHT="72" BORDER="0"></A><P><!--end header--><BR Clear><H1>mem_fun1_t<Result, X, Arg></H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "functors.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "type.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left><Img src = "adaptors.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right></TD></TR><TR><TD Align=left VAlign=top><b>Categories</b>: functors, adaptors</TD><TD Align=right VAlign=top><b>Component type</b>: type</TD></TR></Table><h3>Description</h3><tt>Mem_fun1_t</tt> is an adaptor for member functions. If <tt>X</tt> is some classwith a member function <tt>Result X::f(Arg)</tt> (that is, a member functionthat takes one argument of type <tt>Arg</tt> and that returns a value of type<tt>Result</tt> <A href="#1">[1]</A>), then a <tt>mem_fun1_t<Result, X, Arg></tt> is a<A href="functors.html">function object</A> adaptor that makes it possible to call <tt>f</tt> as ifit were an ordinary function instead of a member function.<P><tt>Mem_fun1_t<Result, X, Arg></tt>'s constructor takes a pointer to one of<tt>X</tt>'s member functions. Then, like all function objects, <tt>mem_fun1_t</tt>has an <tt>operator()</tt> that allows the <tt>mem_fun1_t</tt> to be invoked withordinary function call syntax. In this case, <tt>mem_fun1_t</tt>'s<tt>operator()</tt> takes two arguments; the first is of type <tt>X*</tt> and thesecond is of type <tt>Arg</tt>.<P>If <tt>F</tt> is a <tt>mem_fun1_t</tt> that was constructed to use the memberfunction <tt>X::f</tt>, and if <tt>x</tt> is a pointer of type <tt>X*</tt> and <tt>a</tt> is avalue of type <tt>Arg</tt>, then the expression <tt>F(x, a)</tt> is equivalent tothe expression <tt>x->f(a)</tt>. The difference is simply that <tt>F</tt> can bepassed to STL algorithms whose arguments must be function objects.<P><tt>Mem_fun1_t</tt> is one of a family of member function adaptors. These adaptors are useful if you want to combine generic programmingwith inheritance and polymorphism, since, in C++, polymorphisminvolves calling member functions through pointers or references.<P>As with many other adaptors, it is usually inconvenient to use <tt>mem_fun1_t</tt>'s constructor directly. It is usually better to usethe helper function <tt>mem_fun</tt> <A href="#2">[2]</A> instead.<h3>Example</h3><pre>struct Operation { virtual double eval(double) = 0;};struct Square : public Operation { double eval(double x) { return x * x; }};struct Negate : public Operation { double eval(double x) { return -x; }};int main() { <A href="Vector.html">vector</A><Operation*> operations; <A href="Vector.html">vector</A><double> operands; operations.push_back(new Square); operations.push_back(new Square); operations.push_back(new Negate); operations.push_back(new Negate); operations.push_back(new Square); operands.push_back(1); operands.push_back(2); operands.push_back(3); operands.push_back(4); operands.push_back(5); <A href="transform.html">transform</A>(operations.begin(), operations.end(), operands.begin(), <A href="ostream_iterator.html">ostream_iterator</A><double>(cout, "\n"), mem_fun(Operation::eval));}</pre><h3>Definition</h3>Defined in the standard header <A href="functional">functional</A>, and in the nonstandardbackward-compatibility header <A href="function.h">function.h</A>.<h3>Template parameters</h3><Table border><TR><TH>Parameter</TH><TH>Description</TH><TH>Default</TH></TR><TR><TD VAlign=top><tt>Result</tt></TD><TD VAlign=top>The member function's return type.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>X</tt></TD><TD VAlign=top>The class whose member function the <tt>mem_fun1_t</tt> invokes.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>Arg</tt></TD><TD VAlign=top>The member function's argument type.</TD><TD VAlign=top> </TD></tr></table><h3>Model of</h3><A href="AdaptableBinaryFunction.html">Adaptable Binary Function</A><h3>Type requirements</h3><UL><LI><tt>X</tt> has at least one member function that takes a single argument of type <tt>Arg</tt> and that returns a value of type <tt>Result</tt>. <A href="#1">[1]</A></UL><h3>Public base classes</h3><tt><A href="binary_function.html">binary_function</A><X*, Arg, Result></tt><h3>Members</h3><Table border><TR><TH>Member</TH><TH>Where defined</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>first_argument_type</tt></TD><TD VAlign=top> <A href="AdaptableBinaryFunction.html">Adaptable Binary Function</A></TD><TD VAlign=top>The type of the first argument: <tt>X*</tt></TD></TR><TR><TD VAlign=top><tt>second_argument_type</tt></TD><TD VAlign=top> <A href="AdaptableBinaryFunction.html">Adaptable Binary Function</A></TD><TD VAlign=top>The type of the second argument: <tt>Arg</tt></TD></TR><TR><TD VAlign=top><tt>result_type</tt></TD><TD VAlign=top> <A href="AdaptableBinaryFunction.html">Adaptable Binary Function</A></TD><TD VAlign=top>The type of the result: <tt>Result</tt></TD></TR><TR><TD VAlign=top><pre>Result operator()(X* x, Arg a) const</pre></TD><TD VAlign=top> <A href="BinaryFunction.html">Binary Function</A></TD><TD VAlign=top>Function call operator. Invokes <tt>x->f(a)</tt>, where <tt>f</tt> is the member function that was passed to the constructor.</TD></TR><TR><TD VAlign=top><pre>explicit mem_fun1_t(Result (X::*f)(Arg))</pre></TD><TD VAlign=top><tt>mem_fun1_t</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><pre>template <class Result, class X, class Arg>mem_fun1_t<Result, X, Arg>mem_fun(Result (X::*f)(Arg)); <A href="#2">[2]</A></pre></TD><TD VAlign=top><tt>mem_fun1_t</tt></TD><TD VAlign=top>See below.</TD></tr></table><h3>New members</h3>These members are not defined in the <A href="AdaptableBinaryFunction.html">Adaptable Binary Function</A>requirements, but are specific to <tt>mem_fun1_t</tt>.<Table border><TR><TH>Member</TH><TH>Description</TH></TR><TR><TD VAlign=top><pre>explicit mem_fun1_t(Result (X::*f)(Arg))</pre></TD><TD VAlign=top>The constructor. Creates a <tt>mem_fun1_t</tt> that calls the member function <tt>f</tt>.</TD></TR><TR><TD VAlign=top><pre>template <class Result, class X, class Arg>mem_fun1_t<Result, X, Arg>mem_fun(Result (X::*f)(Arg)); <A href="#2">[2]</A></pre></TD><TD VAlign=top>If <tt>f</tt> is of type <tt>Result (X::*)(Arg)</tt> then <tt>mem_fun(f)</tt> is thesame as <tt>mem_fun1_t<Result, X, Arg>(f)</tt>, but is more convenient. This is aglobal function, not a member function.</TD></tr></table><h3>Notes</h3><P><A name="1">[1]</A>The type <tt>Result</tt> is permitted to be <tt>void</tt>. That is, thisadaptor may be used for functions that return no value. However, thispresents implementation difficulties. According to the draft C++standard, it is possible to return from a <tt>void</tt> function by writing<tt>return void</tt> instead of just <tt>return</tt>. At present, however (early1998), very few compilers support that feature. As a substitute,then, <tt>mem_fun1_t</tt> uses partial specialization to support <tt>void</tt> memberfunctions. If your compiler has not implemented partialspecialization, then you will not be able to use <tt>mem_fun1_t</tt> withmember functions whose return type is <tt>void</tt>.<P><A name="2">[2]</A>This helper function was called <tt>mem_fun1</tt> in drafts of the C++standard, but it is called <tt>mem_fun</tt> in the final standard. Thisimplementation provides both versions for backward compatibility, but<tt>mem_fun1</tt> will be removed in a future release.<h3>See also</h3><tt><A href="mem_fun_t.html">mem_fun_t</A></tt>, <tt><A href="mem_fun_ref_t.html">mem_fun_ref_t</A></tt>, <tt><A href="mem_fun1_ref_t.html">mem_fun1_ref_t</A></tt><!-- start footer --><!-- Footer Begins --><STYLE TYPE="text/css"><!--TD.footer, TD.footer A{ font-family: Arial, helvetica, sans-serif; font-size: 8pt;}A.home {font-family: Arial, helvetica, sans-serif;}--></STYLE><P><A CLASS="home" HREF="index.html">STL Home</A><P><TABLE WIDTH="600" CELLPADDING="0" CELLPADDING="0" BORDER="0"> <TR> <TD ALIGN="RIGHT" CLASS="footer"><A HREF="/company_info/terms.html" TARGET="_top">terms of use</A> | <A HREF="/company_info/privacy.html" TARGET="_top">privacy policy</A></TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/cgi-bin/feedback/" TARGET="_top">contact us</A></TD> </TR><TR> <TD ALIGN="RIGHT" CLASS="footer">Copyright © 1993-2003 Silicon Graphics, Inc. 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