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annotate doc/misc/html/examples/ffcalc.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 <HTML>
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3 <HEAD>
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4 <TITLE>Four Function Calculator</TITLE>
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5 </HEAD>
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6
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7
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8 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
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9 TEXT="#000000" LINK="#0033CC"
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10 VLINK="#CC0033" ALINK="#CC0099">
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11
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12 <P>
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13 <IMG ALIGN="right" SRC="../images/agrsl6c.gif" ALT="AnaGram"
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14 WIDTH=124 HEIGHT=30 >
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15 <BR CLEAR="all">
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16 Back to <A HREF="../index.html">Index</A>
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17 <P>
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18 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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19 WIDTH=1010 HEIGHT=2 >
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20 <P>
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21
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22 <H1>Four Function Calculator</H1>
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23
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24 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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25 WIDTH=1010 HEIGHT=2 >
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26 <P>
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27 <H2>Introduction</H2>
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28 <P>
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29 <tt>ffcalc.syn</tt> implements a simple four function
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30 calculator. The
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31 calculator has 52 registers, labeled 'a' through 'z' and 'A'
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32 through 'Z'. <tt>ffcalc</tt> evaluates arithmetic expressions and
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33 assignment statements and prints the results. The
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34 expressions may contain '<CODE>+</CODE>', '<CODE>-</CODE>',
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35 '<CODE>*</CODE>', and '<CODE>/</CODE>' operators as
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36 well as parentheses. In addition, <tt>ffcalc</tt> supports
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37 the free
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38 use of white space and C style comments in the input. It
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39 also includes syntax error handling, including a diagnostic
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40 message, and resynchronization.
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41 <P>
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42 <tt>ffcalcmx.syn</tt> is a simple variation on
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43 <tt>ffcalc.syn</tt>. The only
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44 difference between the two grammars is that <tt>ffcalcx</tt> uses a
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45 deliberately ambiguous grammar for expressions, with
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46 precedence statements to resolve the ambiguities.
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47 <P>
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48
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49 <H2>Building FFCALC</H2>
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50 To build a working copy of <tt>ffcalc</tt>, you need to
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51 carry out the following steps:
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52 <UL>
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53 <LI> 1. Run Anagram and build a parser for <tt>ffcalc.syn</tt>. </LI>
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54 <LI> 2. Using your C compiler, compile and link <tt>ffcalc.c</tt>. </LI>
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55 </UL>
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56 <P>
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57
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58 <H2>Running FFCALC</H2>
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59 <tt>ffcalc</tt> reads expressions and assignment statements from
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60 stdin. You may either type input directly, or provide input
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61 by using file redirection. The file <tt>test.ffc</tt> has been
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62 provided as a sample.
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63 <P>
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64 Run <tt>ffcalc</tt> from the command line and type an
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65 arithmetic expression or assignment
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66 statement to be evaluated. <tt>ffcalc</tt> will accept addition,
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67 subtraction, multiplication and division operations, as well
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68 as unary negation, using floating point arithmetic. It
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69 respects the conventional order of operations and allows the
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70 use of parentheses to override the natural order of
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71 computation. You may use spaces, tabs, and C-style comments
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72 freely. You may use variable names consisting of a single
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73 upper or lower case letter.
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74 <P>
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75 Each expression or assignment statement must be terminated
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76 by a newline. Note that <tt>ffcalc</tt>, unlike
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77 <tt>rcalc</tt>, does not explicitly check
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78 for division by zero.
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79 </P>
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80
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81 <BR>
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82
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83 <IMG ALIGN="bottom" SRC="../images/rbline6j.gif" ALT="----------------------"
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84 WIDTH=1010 HEIGHT=2 >
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85 <P>
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86 <IMG ALIGN="right" SRC="../images/pslrb6d.gif" ALT="Parsifal Software"
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87 WIDTH=181 HEIGHT=25>
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88 <BR CLEAR="right">
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89 <P>
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90 Back to <A HREF="../index.html">Index</A>
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91 <P>
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92 <ADDRESS><FONT SIZE="-1">
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93 AnaGram parser generator - examples<BR>
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94 Four Function Calculator<BR>
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95 Copyright &copy; 1993-1999, Parsifal Software. <BR>
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96 All Rights Reserved.<BR>
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97 </FONT></ADDRESS>
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98
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99 </BODY>
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100 </HTML>
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101