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<HTML><!-- -- Copyright (c) 1996-1999 -- Silicon Graphics Computer Systems, Inc. -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. Silicon Graphics makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- -- Copyright (c) 1994 -- Hewlett-Packard Company -- -- Permission to use, copy, modify, distribute and sell this software -- and its documentation for any purpose is hereby granted without fee, -- provided that the above copyright notice appears in all copies and -- that both that copyright notice and this permission notice appear -- in supporting documentation. 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It is provided "as is" without express or implied warranty. -- --><Head><Title>unary_compose<AdaptableUnaryFunction1,AdaptableUnaryFunction2></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>unary_compose<AdaptableUnaryFunction1,AdaptableUnaryFunction2></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>Unary_compose</tt> is a <A href="functors.html">function object</A> adaptor. If <tt>f</tt> and <tt>g</tt> are both<A href="AdaptableUnaryFunction.html">Adaptable Unary Functions</A>, and if <tt>g</tt>'s return type is convertibleto <tt>f</tt>'s argument type, then <tt>unary_compose</tt> can be used to create afunction object <tt>h</tt> such that <tt>h(x)</tt> is the same as <tt>f(g(x))</tt>. <A href="#1">[1]</A> Aswith other function object adaptors, the easiest way to create a<tt>unary_compose</tt> is to use the helper function <tt>compose1</tt>. It ispossible to call <tt>unary_compose</tt>'s constructor directly, but thereis usually no reason to do so.<h3>Example</h3>Calculates the negative of the sines of the elements in a vector, where the elementsare angles measured in degrees. Since the C library function <tt>sin</tt>takes its arguments in radians, this operation is the composition ofthree operations: negation, <tt>sin</tt>, and the conversion of degrees to radians.<pre>vector<double> angles;vector<double> sines;const double pi = 3.14159265358979323846;...assert(sines.size() >= angles.size());transform(angles.begin(), angles.end(), sines.begin(), compose1(<A href="negate.html">negate</A><double>(), compose1(<A href="ptr_fun.html">ptr_fun</A>(sin), <A href="binder2nd.html">bind2nd</A>(<A href="times.html">multiplies</A><double>(), pi / 180.))));</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>. The <tt>unary_compose</tt>class is an SGI extension; it is not part of the C++ standard.<h3>Template parameters</h3><Table border><TR><TH>Parameter</TH><TH>Description</TH><TH>Default</TH></TR><TR><TD VAlign=top><tt>AdaptableUnaryFunction1</tt></TD><TD VAlign=top>The type of the first operand in the function composition operation. That is, if the composition is written <tt>f o g</tt> <A href="#1">[1]</A>, then <tt>AdaptableUnaryFunction1</tt> is the type of the function object <tt>f</tt>.</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>AdaptableUnaryFunction2</tt></TD><TD VAlign=top>The type of the second operand in the function composition operation. That is, if the composition is written <tt>f o g</tt> <A href="#1">[1]</A>, then <tt>AdaptableUnaryFunction1</tt> is the type of the function object <tt>g</tt>.</TD><TD VAlign=top> </TD></tr></table><h3>Model of</h3><A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A><h3>Type requirements</h3><tt>AdaptableUnaryFunction1</tt> and <tt>AdaptableUnaryFunction2</tt> must bothbe models of <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>. <tt>AdaptableUnaryFunction2::result_type</tt> must be convertible to<tt>AdaptableUnaryFunction1::argument_type</tt>.<h3>Public base classes</h3><pre><A href="unary_function.html">unary_function</A><AdaptableUnaryFunction2::argument_type, AdaptableUnaryFunction1::result_type></pre><h3>Members</h3><Table border><TR><TH>Member</TH><TH>Where defined</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>argument_type</tt></TD><TD VAlign=top> <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A></TD><TD VAlign=top>The type of the function object's argument:<tt>AdaptableUnaryFunction2::argument_type</tt>.</TD></TR><TR><TD VAlign=top><tt>result_type</tt></TD><TD VAlign=top> <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A></TD><TD VAlign=top>The type of the result: <tt>AdaptableUnaryFunction1::result_type</tt></TD></TR><TR><TD VAlign=top><pre>unary_compose(const AdaptableUnaryFunction1& f, const AdaptableUnaryFunction2& g);</pre></TD><TD VAlign=top><tt>unary_compose</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><pre>template <class <A href="AdaptableUnaryFunction.html">AdaptableUnaryFunction</A>1, class <A href="AdaptableUnaryFunction.html">AdaptableUnaryFunction</A>2>unary_compose<AdaptableUnaryFunction1, AdaptableUnaryFunction2> compose1(const AdaptableUnaryFunction1& op1, const AdaptableUnaryFunction2& op2);</pre></TD><TD VAlign=top><tt>unary_compose</tt></TD><TD VAlign=top>See below.</TD></tr></table><h3>New members</h3>These members are not defined in the <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>requirements, but are specific to <tt>unary_compose</tt>.<Table border><TR><TH>Member</TH><TH>Description</TH></TR><TR><TD VAlign=top><pre>unary_compose(const AdaptableUnaryFunction1& f, const AdaptableUnaryFunction2& g);</pre></TD><TD VAlign=top>The constructor. Constructs a <tt>unary_compose</tt> object that representsthe function object <tt>f o g</tt>. <A href="#1">[1]</A></TD></TR><TR><TD VAlign=top><pre>template <class <A href="AdaptableUnaryFunction.html">AdaptableUnaryFunction</A>1, class <A href="AdaptableUnaryFunction.html">AdaptableUnaryFunction</A>2>unary_compose<AdaptableUnaryFunction1, AdaptableUnaryFunction2> compose1(const AdaptableUnaryFunction1& op1, const AdaptableUnaryFunction2& op2);</pre></TD><TD VAlign=top>Creates a <tt>unary_compose</tt> object. If <tt>f</tt> and <tt>g</tt> are, respectively, of classes<tt>AdaptableUnaryFunction1</tt> and <tt>AdaptableUnaryFunction2</tt>, then<tt>compose1(f, g)</tt> is equivalent to <tt>unary_compose<AdaptableUnaryFunction1, AdaptableUnaryFunction2>(f, g)</tt>,but is more convenient. This is a global function, not a member function.</TD></tr></table><h3>Notes</h3><P><A name="1">[1]</A>This operation is called function composition, hencethe name <tt>unary_compose</tt>. It is often represented in mathematicsas the operation <tt>f o g</tt>, where <tt>f o g</tt> is a function such that<tt>(f o g)(x) == f(g(x))</tt>. Function composition is a very importantconcept in algebra. It is also extremely important as a methodof building software components out of other components, becauseit makes it possible to construct arbitrarily complicated functionobjects out of simple ones.<h3>See also</h3>The <A href="functors.html">function object overview</A>, <tt><A href="binary_compose.html">binary_compose</A></tt>, <tt><A href="binder1st.html">binder1st</A></tt>, <tt><A href="binder2nd.html">binder2nd</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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