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<H1>Roman Numeral Calculator</H1>
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<H2>Introduction</H2>
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          <tt>rcalc</tt> is a simple four function desk calculator program
          which accepts its input and displays its output in Roman
          numerals. The source code for <tt>rcalc</tt> is completely contained
          in the file <tt>rcalc.syn</tt>.

          <tt>rcalc</tt> illustrates the following AnaGram features:
<UL>
<LI>       pointer input </LI>
<LI>       <tt>SYNTAX_ERROR</tt> macro </LI>
<LI>       context tracking </LI>
</UL>
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<H2>     Building RCALC </H2>
          To build a working copy of <tt>rcalc</tt>, you need to carry out the
          following steps:
<UL>
<LI>       1.  Run Anagram and build a parser for <tt>rcalc</tt> </LI>
<LI>       2.  Using your C compiler, compile and link <tt>rcalc.c</tt>. </LI>
</UL>
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<H2>     Running RCALC </H2>
          When you run <tt>rcalc</tt> (from the command line), it will
          display a '<CODE>#</CODE>' prompt. Type an
          arithmetic expression in Roman numerals, using either upper
          or lower case letters. <tt>rcalc</tt> will accept addition,
          subtraction, multiplication and division operations, as well
          as unary negation, using integer arithmetic. It respects the
          conventional order of operations. You may use spaces and tabs
          freely when you type the expression and parentheses to
          override the natural order of computation. You may use the
          word <tt>NIHIL</tt> to represent zero.
<P>
          When you have typed your expression, press Enter. <tt>rcalc</tt> will
          parse your expression, and if it has no syntax errors, <tt>rcalc</tt>
          will display the result in Roman numerals. If there is a
          syntax error, or if you tried to divide by zero, <tt>rcalc</tt> will
          display a diagnostic message, showing the location of the
          error. You may exit the program by pressing Enter at the
          prompt.


<BR><BR><BR>
<H2>     Theory of Operation </H2>
          <tt>rcalc</tt>, like Gaul, is divided into three parts: reading
          input, interpreting Roman numerals, and evaluating
          expressions.
<P>
          In <tt>rcalc</tt>, the main program, written in C, displays a prompt,
          reads a line of input, calls the parser to interpret it, and
          loops until it encounters end of file. The <tt>rcalc</tt> parser uses
          "pointer input" to parse a string already in memory. The
          main program needs only to set the "pointer" field in the
          parser control block to point to the string before calling
          the parser.
<P>
          The syntax for the Roman numerals consists of
          straightforward enumeration of the possibilities. At every
          level but the thousands, there are a number of special
          cases, and at every level including the thousands there is
          the possibility of repetition. The major complicating factor
          is that every field, from the thousands to the units, is
          optional, but at least one field has to be present.
<P>
          The expression logic is simply the conventional syntax for
          the basic arithmetic functions.
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<ADDRESS><FONT SIZE="-1"><BR><BR>
                  AnaGram parser generator - examples<BR>
                  Roman Numeral Calculator <BR>
                  Copyright (c) MCMXCIII-MCMXCIX, Parsifal Software. <BR>
                  All Rights Reserved. <BR>
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author	David A. Holland
date	Sun, 26 Apr 2009 17:58:26 -0400
parents	13d2b8934445
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