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<Head>
<Title>Default Constructible</Title>
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<H1>Default Constructible</H1>
<Table CellPadding=0 CellSpacing=0 width=100%>
<TR>
<TD Align=left><Img src = "utilities.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
<TD Align=right><Img src = "concept.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
</TR>
<TR>
<TD Align=left VAlign=top><b>Category</b>: utilities</TD>
<TD Align=right VAlign=top><b>Component type</b>: concept</TD>
</TR>
</Table>
<h3>Description</h3>
A type is DefaultConstructible if it has a default constructor,
that is, if it is possible to construct an object of that type
without initializing the object to any particular value.
<h3>Refinement of</h3>
<h3>Associated types</h3>
<h3>Notation</h3>
<Table>
<TR>
<TD VAlign=top>
<tt>X</tt>
</TD>
<TD VAlign=top>
A type that is a model of DefaultConstructible
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>x</tt>
</TD>
<TD VAlign=top>
An object of type <tt>X</tt>
</TD>
</tr>
</table>
<h3>Definitions</h3>
<h3>Valid expressions</h3>
<Table border>
<TR>
<TH>
Name
</TH>
<TH>
Expression
</TH>
<TH>
Type requirements
</TH>
<TH>
Return type
</TH>
</TR>
<TR>
<TD VAlign=top>
Default constructor
</TD>
<TD VAlign=top>
<tt>X()</tt>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
<tt>X</tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
Default constructor
</TD>
<TD VAlign=top>
<tt>X x;</tt> <A href="#1">[1]</A>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
</TD>
</tr>
</table>
<h3>Expression semantics</h3>
<Table border>
<TR>
<TH>
Name
</TH>
<TH>
Expression
</TH>
<TH>
Precondition
</TH>
<TH>
Semantics
</TH>
<TH>
Postcondition
</TH>
</TR>
<TR>
<TD VAlign=top>
Default constructor
</TD>
<TD VAlign=top>
<tt>X()</tt>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
</TD>
</TR>
<TR>
<TD VAlign=top>
Default constructor
</TD>
<TD VAlign=top>
<tt>X x;</tt>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
</TD>
</tr>
</table>
<h3>Complexity guarantees</h3>
<h3>Models</h3>
<UL>
<LI>
int
<LI>
<tt><A href="Vector.html">vector</A><double></tt>
</UL>
<h3>Notes</h3>
<P><A name="1">[1]</A>
The form <tt>X x = X()</tt> is not guaranteed to be a valid expression,
because it uses a copy constructor. A type that is
DefaultConstructible is not necessarily <A href="Assignable.html">Assignable</A>
<h3>See also</h3>
<A href="Assignable.html">Assignable</A>
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