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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>pointer_to_unary_function<Arg, Result></Title><!-- Generated by htmldoc --></HEAD><BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" ALINK="#ff0000"> <IMG SRC="CorpID.gif" ALT="SGI" HEIGHT="43" WIDTH="151"> <!--end header--><BR Clear><H1>pointer_to_unary_function<Arg, Result></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 = "39" ></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>Pointer_to_unary_function</tt> is a <A href="functors.html">function object</A> adaptor thatallows a function pointer <tt>Result (*f)(Arg)</tt> to be treated as an<A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>. That is: if <tt>F</tt> is a<tt>pointer_to_unary_function<Arg, Result></tt> that was initializedwith an underlying function pointer <tt>f</tt> of type<tt>Result (*)(Arg)</tt>, then <tt>F(x)</tt> calls the function <tt>f(x)</tt>.The difference between <tt>f</tt> and <tt>F</tt> is that <tt>pointer_to_unary_function</tt> is an <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>,<i>i.e.</i> it defines the nested <tt>typedef</tt>s <tt>argument_type</tt>and <tt>result_type</tt>. <P>Note that a function pointer of type <tt>Result (*)(Arg)</tt> is a perfectlygood <A href="UnaryFunction.html">Unary Function</A> object, and may be passed to an STL algorithmthat expects an argument that is a <A href="UnaryFunction.html">Unary Function</A>. The onlyreason for using the <tt>pointer_to_unary_function</tt> object is if you needto use an ordinary function in a context that requires an <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A>, <i>e.g.</i> as the argument of a function objectadaptor.<P>Most of the time, you need not declare an object of type<tt>pointer_to_unary_function</tt> directly. It is almost always easier toconstruct one using the <tt><A href="ptr_fun.html">ptr_fun</A></tt> function.<h3>Example</h3>The following code fragment replaces all of the numbers in a range with theirabsolute values, using the standard library function <tt>fabs</tt>.There is no need to use a <tt>pointer_to_unary_function</tt>adaptor in this case.<pre><A href="transform.html">transform</A>(first, last, first, fabs);</pre>The following code fragment replaces all of the numbers in a range with thenegative of their absolute values. In this case we are composing<tt>fabs</tt> and <tt><A href="negate.html">negate</A></tt>. This requires that <tt>fabs</tt> be treated as an<A href="AdaptableUnaryFunction.html">adaptable unary function</A>, so we do need to use a<tt>pointer_to_unary_function</tt> adaptor.<pre><A href="transform.html">transform</A>(first, last, first, <A href="unary_compose.html">compose1</A>(<A href="negate.html">negate</A><double>, <A href="ptr_fun.html">ptr_fun</A>(fabs)));</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>Arg</tt></TD><TD VAlign=top>The function object's argument type</TD><TD VAlign=top> </TD></TR><TR><TD VAlign=top><tt>Result</tt></TD><TD VAlign=top>The function object's result type</TD><TD VAlign=top> </TD></tr></table><h3>Model of</h3><A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A><h3>Type requirements</h3><UL><LI><tt>Arg</tt> is <A href="Assignable.html">Assignable</A>.<LI><tt>Result</tt> is <A href="Assignable.html">Assignable</A>.</UL><h3>Public base classes</h3><tt><A href="unary_function.html">unary_function</A><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>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>Arg</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>Result</tt></TD></TR><TR><TD VAlign=top><tt>result_type operator()(argument_type x)</tt></TD><TD VAlign=top> <A href="UnaryFunction.html">Unary Function</A></TD><TD VAlign=top>Function call operator.</TD></TR><TR><TD VAlign=top><tt>pointer_to_unary_function(Result (*f)(Arg))</tt></TD><TD VAlign=top><tt>pointer_to_unary_function</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><tt>pointer_to_unary_function()</tt></TD><TD VAlign=top><tt>pointer_to_unary_function</tt></TD><TD VAlign=top>See below.</TD></TR><TR><TD VAlign=top><pre>template <class Arg, class Result>pointer_to_unary_function<Arg, Result> ptr_fun(Result (*x)(Arg));</pre></TD><TD VAlign=top><tt>pointer_to_unary_function</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>pointer_to_unary_function</tt>. <Table border><TR><TH>Member</TH><TH>Description</TH></TR><TR><TD VAlign=top><tt>pointer_to_unary_function(Result (*f)(Arg))</tt></TD><TD VAlign=top>The constructor. Creates a <tt>pointer_to_unary_function</tt> whose underlying function is <tt>f</tt>.</TD></TR><TR><TD VAlign=top><tt>pointer_to_unary_function()</tt></TD><TD VAlign=top>The default constructor. This creates a <tt>pointer_to_unary_function</tt> that does not have an underlying C function, and that therefore cannot actually be called.</TD></TR><TR><TD VAlign=top><pre>template <class Arg, class Result>pointer_to_unary_function<Arg, Result> ptr_fun(Result (*x)(Arg));</pre></TD><TD VAlign=top>If <tt>f</tt> is of type <tt>Result (*)(Arg)</tt> then<tt>ptr_fun(f)</tt> is equivalent to<tt>pointer_to_unary_function<Arg,Result>(f)</tt>,but more convenient. This is a global function, not a member.</TD></tr></table><h3>Notes</h3><h3>See also</h3><tt><A href="pointer_to_binary_function.html">pointer_to_binary_function</A></tt>, <tt><A href="ptr_fun.html">ptr_fun</A></tt>, <A href="AdaptableUnaryFunction.html">Adaptable Unary Function</A><!--start footer--> <HR SIZE="6"><A href="http://www.sgi.com/"><IMG SRC="surf.gif" HEIGHT="54" WIDTH="54" ALT="[Silicon Surf]"></A><A HREF="index.html"><IMG SRC="stl_home.gif" HEIGHT="54" WIDTH="54" ALT="[STL Home]"></A><BR><FONT SIZE="-2"><A href="http://www.sgi.com/Misc/sgi_info.html" TARGET="_top">Copyright © 1999 Silicon Graphics, Inc.</A> All Rights Reserved.</FONT><FONT SIZE="-3"><a href="http://www.sgi.com/Misc/external.list.html" TARGET="_top">TrademarkInformation</A></FONT><P></BODY></HTML> ⌨️ 快捷键说明
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