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<Title>Generator</Title>
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<H1>Generator</H1>
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<TD Align=left><Img src = "functors.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
<TD Align=right><Img src = "concept.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
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<TR>
<TD Align=left VAlign=top><b>Category</b>: functors</TD>
<TD Align=right VAlign=top><b>Component type</b>: concept</TD>
</TR>
</Table>
<h3>Description</h3>
A Generator is a kind of <A href="functors.html">function object</A>: an object that is called
as if it were an ordinary C++ function. A Generator is called with no
arguments.
<h3>Refinement of</h3>
<A href="Assignable.html">Assignable</A>
<h3>Associated types</h3>
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<TD VAlign=top>
Result type
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The type returned when the Generator is called
</TD>
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<h3>Notation</h3>
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<TR>
<TD VAlign=top>
<tt>F</tt>
</TD>
<TD VAlign=top>
A type that is a model of Generator
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>Result</tt>
</TD>
<TD VAlign=top>
The result type of <tt>F</tt>
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<TR>
<TD VAlign=top>
<tt>f</tt>
</TD>
<TD VAlign=top>
Object of type <tt>F</tt>
</TD>
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<h3>Definitions</h3>
The <i>range</i> of a Generator is the set of all possible value that it
may return.
<h3>Valid expressions</h3>
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<TH>
Name
</TH>
<TH>
Expression
</TH>
<TH>
Type requirements
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<TH>
Return type
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<TR>
<TD VAlign=top>
Function call
</TD>
<TD VAlign=top>
<tt>f()</tt>
</TD>
<TD VAlign=top>
</TD>
<TD VAlign=top>
<tt>Result</tt>
</TD>
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<h3>Expression semantics</h3>
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<TH>
Name
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<TH>
Expression
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Precondition
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<TH>
Semantics
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Postcondition
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<TD VAlign=top>
Function call
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<TD VAlign=top>
<tt>f()</tt>
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<TD VAlign=top>
</TD>
<TD VAlign=top>
Returns some value of type <tt>Result</tt> <A href="#1">[1]</A>
</TD>
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The return value is in <tt>f</tt>'s range.
</TD>
</tr>
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<h3>Complexity guarantees</h3>
<h3>Invariants</h3>
<h3>Models</h3>
<UL>
<LI>
<tt>Result (*)()</tt>
</UL>
<h3>Notes</h3>
<P><A name="1">[1]</A>
Two different invocations of <tt>f</tt> may return different results:
a Generator may refer to local state, perform I/O, and
so on. The expression <tt>f()</tt> is permitted to change <tt>f</tt>'s state; <tt>f</tt>
might, for example, represent a pseudo-random number generator.
<h3>See also</h3>
<A href="functors.html">Function Object overview</A>, <A href="UnaryFunction.html">Unary Function</A>, <A href="BinaryFunction.html">Binary Function</A>,
<A href="AdaptableGenerator.html">Adaptable Generator</A>
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