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<H1>construct</H1>

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<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>
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<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 &lt;class T1, class T2&gt; void construct(T1* p, const T2&amp; value);
</pre>                   
<h3>Description</h3>
In C++, the operator <tt>new</tt> allocates memory for an object and then
creates 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> is
a 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 location
pointed to by <tt>p</tt>.  The argument <tt>value</tt> is passed as an argument to 
<tt>T1</tt>'s constructor.
<h3>Definition</h3>
Declared in <A href="algo.h">algo.h</A>.  The implementation is in <A href="algobase.h" tppabs="http://www.sgi.com/Technology/STL/algobase.h">algobase.h</A>.
<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 memory
allocation primitives, is used to implement container classes.
<h3>See also</h3>
<A href="Allocators.html">Allocators</A>, <tt><A href="destroy.html" tppabs="http://www.sgi.com/Technology/STL/destroy.shtml">destroy</A></tt>, <tt><A href="uninitialized_copy.html" tppabs="http://www.sgi.com/Technology/STL/uninitialized_copy.shtml">uninitialized_copy</A></tt>, 
<tt><A href="uninitialized_fill.html">uninitialized_fill</A></tt>, <tt><A href="uninitialized_fill_n.html" tppabs="http://www.sgi.com/Technology/STL/uninitialized_fill_n.shtml">uninitialized_fill_n</A></tt>,
<tt><A href="raw_storage_iterator.html">raw_storage_iterator</A></tt>

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