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annotate doc/misc/html/examples/rcalc.html @ 21:1c9dac05d040

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Add lint-style FALLTHROUGH annotations to fallthrough cases. (in the parse engine and thus the output code) Document this, because the old output causes warnings with gcc10.
author David A. Holland
date Mon, 13 Jun 2022 00:04:38 -0400
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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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2 <TITLE>Roman Numeral Calculator</TITLE>
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3 </HEAD>
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4
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5
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6 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
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7 TEXT="#000000" LINK="#0033CC"
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8 VLINK="#CC0033" ALINK="#CC0099">
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9
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10 <P>
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11 <IMG ALIGN="right" SRC="../images/agrsl6c.gif" ALT="AnaGram"
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12 WIDTH=124 HEIGHT=30 >
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13 <BR CLEAR="all">
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14 Back to <A HREF="../index.html">Index</A>
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15 <P>
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16 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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17 WIDTH=1010 HEIGHT=2 >
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18 <P>
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19
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20 <H1>Roman Numeral Calculator</H1>
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21 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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22 WIDTH=1010 HEIGHT=2 >
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23 <P>
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24 <H2>Introduction</H2>
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25 <P>
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26 <tt>rcalc</tt> is a simple four function desk calculator program
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27 which accepts its input and displays its output in Roman
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28 numerals. The source code for <tt>rcalc</tt> is completely contained
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29 in the file <tt>rcalc.syn</tt>.
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30
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31 <tt>rcalc</tt> illustrates the following AnaGram features:
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32 <UL>
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33 <LI> pointer input </LI>
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34 <LI> <tt>SYNTAX_ERROR</tt> macro </LI>
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35 <LI> context tracking </LI>
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36 </UL>
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37 <P>
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38
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39 <H2> Building RCALC </H2>
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40 To build a working copy of <tt>rcalc</tt>, you need to carry out the
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41 following steps:
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42 <UL>
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43 <LI> 1. Run Anagram and build a parser for <tt>rcalc</tt> </LI>
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44 <LI> 2. Using your C compiler, compile and link <tt>rcalc.c</tt>. </LI>
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45 </UL>
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46 <P>
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47
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48 <H2> Running RCALC </H2>
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49 When you run <tt>rcalc</tt> (from the command line), it will
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50 display a '<CODE>#</CODE>' prompt. Type an
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51 arithmetic expression in Roman numerals, using either upper
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52 or lower case letters. <tt>rcalc</tt> will accept addition,
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53 subtraction, multiplication and division operations, as well
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54 as unary negation, using integer arithmetic. It respects the
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55 conventional order of operations. You may use spaces and tabs
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56 freely when you type the expression and parentheses to
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57 override the natural order of computation. You may use the
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58 word <tt>NIHIL</tt> to represent zero.
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59 <P>
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60 When you have typed your expression, press Enter. <tt>rcalc</tt> will
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61 parse your expression, and if it has no syntax errors, <tt>rcalc</tt>
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62 will display the result in Roman numerals. If there is a
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63 syntax error, or if you tried to divide by zero, <tt>rcalc</tt> will
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64 display a diagnostic message, showing the location of the
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65 error. You may exit the program by pressing Enter at the
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66 prompt.
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67
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68
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69 <BR><BR><BR>
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70 <H2> Theory of Operation </H2>
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71 <tt>rcalc</tt>, like Gaul, is divided into three parts: reading
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72 input, interpreting Roman numerals, and evaluating
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73 expressions.
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74 <P>
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75 In <tt>rcalc</tt>, the main program, written in C, displays a prompt,
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76 reads a line of input, calls the parser to interpret it, and
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77 loops until it encounters end of file. The <tt>rcalc</tt> parser uses
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78 "pointer input" to parse a string already in memory. The
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79 main program needs only to set the "pointer" field in the
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80 parser control block to point to the string before calling
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81 the parser.
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82 <P>
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83 The syntax for the Roman numerals consists of
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84 straightforward enumeration of the possibilities. At every
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85 level but the thousands, there are a number of special
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86 cases, and at every level including the thousands there is
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87 the possibility of repetition. The major complicating factor
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88 is that every field, from the thousands to the units, is
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89 optional, but at least one field has to be present.
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90 <P>
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91 The expression logic is simply the conventional syntax for
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92 the basic arithmetic functions.
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93 </P>
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94
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95 <BR>
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96
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97 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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98 WIDTH=1010 HEIGHT=2 >
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99 <P>
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100 <IMG ALIGN="right" SRC="../images/pslrb6d.gif" ALT="Parsifal Software"
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101 WIDTH=181 HEIGHT=25>
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102 <BR CLEAR="right">
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103 <P>
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104 Back to <A HREF="../index.html">Index</A>
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105 <P>
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106 <ADDRESS><FONT SIZE="-1"><BR><BR>
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107 AnaGram parser generator - examples<BR>
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108 Roman Numeral Calculator <BR>
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109 Copyright (c) MCMXCIII-MCMXCIX, Parsifal Software. <BR>
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110 All Rights Reserved. <BR>
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111 </FONT></ADDRESS>
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112
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113 </BODY>
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114 </HTML>
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115
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116