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<TITLE>OpenC++ Reference Manual</TITLE>
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<H1>Metaobject Protocol (MOP)</H1>
<P>
At the meta level, the (base-level) programs are represented by objects
of a few predefined classes (and their subclasses that programmers
define). These objects are called <I>metaobjects</I> because
they are <I>meta</I> representation of the programs. Source-to-source
translation from OpenC++ to C++ is implemented by manipulating those
metaobjects.</P>
<P>
The following several sections show details of such metaobjects.
They reflect
various aspects of programs that are not accessible in C++.
Although most of metaobjects provide means of introspection,
some metaobjects represent a behavioral aspect of the program
and enables to control source-to-source translation of the program.
Here is the list of metaobjects:</P>
<UL>
<LI><A HREF="ptree.html"> <CODE><B>Ptree</B></CODE> </A>metaobjects:
<P>
They represent a parse tree of the program. The parse tree
is implemented as a nested-linked list.</P>
<LI><A HREF="env.html"> <CODE><B>Environment</B></CODE> </A>metaobjects:
<P>
They represent bindings between names and types. Since this
MOP is a compile-time MOP, the runtime values bound to names
are not available at the meta level.</P>
<LI><A HREF="typeinfo.html"> <CODE><B>TypeInfo</B></CODE> </A>metaobjects:
<P>
They represent types that appear in the program. The types
include derived types such as pointer types and reference types
as well as built-in types and class types.</P>
<LI><A HREF="class.html"> <CODE><B>Class</B></CODE> </A>metaobjects:
<P>
As well as they represent class definitions,
they control source-to-source translation of the program.
Programmers may define subclasses of <CODE><B>Class</B></CODE> in order to tailor the translation.</P>
<LI><A HREF="member.html"> <CODE><B>Member</B></CODE> </A>metaobjects:
<P>
They represent class members. They inform whether the member is
a constructor, an inline function, a data member, a public member,
or so forth.</P>
</UL>
<P>
Distinguishing <CODE><B>TypeInfo</B></CODE> metaobjects and <CODE><B>Class</B></CODE> metaobjects
might look like wrong design. But this distinction is needed to handle
derived types. <CODE><B>TypeInfo</B></CODE> metaobjects were introduced to deal with
derived types and fundamental types by using the same kind of metaobjects.</P>
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