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Import AnaGram (near-)release tree into Mercurial.
author David A. Holland
date Sat, 22 Dec 2007 17:52:45 -0500
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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
+<HTML>
+<HEAD>
+<TITLE>Expression Evaluator - Macro preprocessor and C Parser </TITLE>
+</HEAD>
+
+
+<BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
+ TEXT="#000000" LINK="#0033CC"
+ VLINK="#CC0033" ALINK="#CC0099">
+
+<P>
+<IMG ALIGN="right" SRC="../../images/agrsl6c.gif" ALT="AnaGram"
+         WIDTH=124 HEIGHT=30 >
+<BR CLEAR="all">
+Back to :
+<A HREF="../../index.html">Index</A> |
+<A HREF="index.html">Macro preprocessor overview</A>
+<P>
+
+
+<IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
+        WIDTH=1010 HEIGHT=2  >
+<P>
+<H1> Expression Evaluator - Macro preprocessor and C Parser   </H1>
+
+<IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
+        WIDTH=1010 HEIGHT=2  >
+<P>
+<BR>
+
+<H2>Introduction</H2>
+<P>          The Expression Evaluator module, <tt>ex.syn</tt>, exists only to
+          evaluate the conditional expressions in <tt>#if</tt> and
+	  <tt>#elif</tt>
+          statements. The syntax for these expressions has been
+          extracted from a full C syntax and reduced to that which is
+          necessary for this purpose.
+<P>
+          The rules for the evaluation of constant expressions are
+          given in Kernighan and Ritchie, sections A7.19 and A12.5
+<P>
+<BR>
+
+<H2>Theory of Operation</H2>
+          The only unusual feature of this grammar is the
+          interposition of a token called "nonzero" to avoid division
+          by zero. Otherwise the grammar is a conventional expression
+          grammar.
+<P>
+          The parser is implemented as an event driven parser. The
+          initializer is <tt>init_ex()</tt>. The parser itself is
+          <tt>ex()</tt>. The
+          parser has been interfaced to the rest of the program by a
+          class definition, <tt>expression_evaluator</tt>.
+<P>
+          The class definition for <tt>expression_evaluator</tt> is given in
+          <tt>mpp.h</tt>. Each instance of the class has its own parser control
+          block. Therefore the parser makes all of its references
+          indirectly through a pointer, <tt>ex_pcb</tt>. Whenever it is
+          necessary to invoke <tt>init_ex()</tt> or <tt>ex()</tt>,
+          therefore, it is
+          necessary first to make sure <tt>ex_pcb</tt> is correctly set.
+<P>
+          Input to the parser consists of tokens as defined in
+          <tt>token.h</tt>. Since the input does not consist of simple
+          characters, the <b>input values</b> switch is set. The input
+          procedures store the full token into the input_value field
+          of the pcb and the id field into input_code.
+
+<P>
+
+<BR>
+
+
+<IMG ALIGN="bottom" SRC="../../images/rbline6j.gif" ALT="----------------------"
+      WIDTH=1010 HEIGHT=2 >
+<P>
+<IMG ALIGN="right" SRC="../../images/pslrb6d.gif" ALT="Parsifal Software"
+                WIDTH=181 HEIGHT=25>
+<BR CLEAR="right">
+
+<P>
+Back to :
+<A HREF="../../index.html">Index</A> |
+<A HREF="index.html">Macro preprocessor overview</A>
+
+<P>
+<ADDRESS><FONT SIZE="-1">
+                  AnaGram parser generator - examples<BR>
+                  Expression Evaluator - Macro preprocessor and C Parser <BR>
+                  Copyright &copy; 1993-1999, Parsifal Software. <BR>
+                  All Rights Reserved.<BR>
+</FONT></ADDRESS>
+
+</BODY>
+</HTML>
+
+