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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. Hewlett-Packard Company makes no -- representations about the suitability of this software for any -- purpose. It is provided "as is" without express or implied warranty. -- --><Head><Title>construct</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>construct</H1><Table CellPadding=0 CellSpacing=0 width=100%><TR><TD Align=left><Img src = "allocators.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD><TD Align=right><Img src = "function.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD></TR><TR><TD Align=left VAlign=top><b>Category</b>: allocators</TD><TD Align=right VAlign=top><b>Component type</b>: function</TD></TR></Table><h3>Prototype</h3><pre>template <class T1, class T2> void construct(T1* p, const T2& value);</pre> <h3>Description</h3>In C++, the operator <tt>new</tt> allocates memory for an object and thencreates an object at that location by calling a constructor. Occasionally,however, it is useful to separate those two operations. <A href="#1">[1]</A> If <tt>p</tt> isa pointer to memory that has been allocated but not initialized,then <tt>construct(p, value)</tt> creates an object of type <tt>T1</tt> at the locationpointed to by <tt>p</tt>. The argument <tt>value</tt> is passed as an argument to <tt>T1</tt>'s constructor.<h3>Definition</h3>Defined in the standard header <A href="memory">memory</A>, and in the nonstandardbackward-compatibility header <A href="algo.h">algo.h</A>. The <tt>construct</tt> algorithmis no longer part of the C++ standard; it was present in early drafts,and it is retained in this implementation for backward compatibility.<h3>Requirements on types</h3><UL><LI><tt>T1</tt> must have a constructor that takes a single argument of type <tt>T2</tt>.</UL><h3>Preconditions</h3><UL><LI><tt>p</tt> is a valid pointer that points to a region of memory whose size is at least <tt>sizeof(T1)</tt>.<LI>The memory pointed to by <tt>p</tt> is uninitialized. That is, no object has been constructed at the location <tt>p</tt>.</UL><h3>Complexity</h3><h3>Example</h3><pre>double* dp = (double*) malloc(sizeof(double));construct(dp, 3);assert(*dp == 3);</pre><h3>Notes</h3><P><A name="1">[1]</A>In particular, <tt>construct</tt>, along with other low-level memoryallocation primitives, is used to implement container classes.<h3>See also</h3><A href="Allocators.html">Allocators</A>, <tt><A href="destroy.html">destroy</A></tt>, <tt><A href="uninitialized_copy.html">uninitialized_copy</A></tt>, <tt><A href="uninitialized_fill.html">uninitialized_fill</A></tt>, <tt><A href="uninitialized_fill_n.html">uninitialized_fill_n</A></tt>,<tt><A href="raw_storage_iterator.html">raw_storage_iterator</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. All rights reserved.</TD> <TD ALIGN="CENTER" CLASS="footer"> | </TD> <TD ALIGN="LEFT" CLASS="footer"><A HREF="/company_info/trademarks/" TARGET="_top">Trademark Information</A></TD> </TR></TABLE><!-- Footer Ends --><!-- end footer --><P></BODY></HTML> ⌨️ 快捷键说明
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