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annotate doc/misc/html/gtrace.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>AnaGram's Grammar Trace Facility</TITLE>
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5
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6 </HEAD>
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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="RIGHT">
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16 </P>
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17
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18 <P>
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19 Back to <A HREF="index.html">Index</A>
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20 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
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21 WIDTH=1010 HEIGHT=2 >
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22
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23 <H2>AnaGram's Grammar Trace</H2>
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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
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27 <P>
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28
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29 The Grammar Trace facility lets you examine the workings of your
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30 parser in detail, <ITALIC>interactively</ITALIC>. You can use Grammar Trace even
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31 <ITALIC>before</ITALIC> you
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32 write any code to attach to the rules of your grammar, and before actually
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33 building a parser. If you have a test file available, you may prefer to use <A
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34 HREF="ftrace.html"><STRONG>File Trace</STRONG></A>.
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35 <P>
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36 Using the various options associated with this trace
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37 you can set up a representation of the parser state stack and parser
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38 state as they might appear in the course of execution of your
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39 parser. You can then examine the allowable input tokens and the
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40 changes to the state and the state stack caused by any input tokens you
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41 choose.
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42
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43 <IMG ALIGN="right" SRC="gramtr6g.gif" ALT="sample Grammar Trace window"
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44 WIDTH=489 HEIGHT=338 VSPACE=8 HSPACE=8 >
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45
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46
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47 <P>
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48 AnaGram now provides a combo box where you can enter input characters
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49 for a Grammar Trace, in addition to choosing tokens. This means you can
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50 run a Grammar Trace like a <A
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51 HREF="ftrace.html">File Trace</A> where the test file is replaced
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52 by the combo box characters you type. This is a very convenient way
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53 to check out your grammar.
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54 </P>
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55
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56 <BR>
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57
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58 <H3> Starting Grammar Traces:</H3>
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59
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60 A Grammar Trace can be selected from either the Action Menu or the
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61 Control Panel toolbar once your grammar has been analyzed. There are
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62 also prebuilt grammar traces like the Conflict Trace and the
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63 Auxiliary Trace, which can be selected from the Auxiliary Windows
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64 popup menu for certain AnaGram windows or panes.
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65 <P>
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66 Like File Trace, a Grammar Trace presents three principal panes. These
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67 are a Parser Stack pane on the left, an Allowable Input pane on the
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68 right, and a Rule Stack pane at the bottom.
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69 <P>
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70 Initially, the Parser Stack will consist of a single line, which
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71 represents the initial configuration of your parser. The first column
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72 will show zero, which is the value of the parser stack
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73 index. The second column will show the state number of the parser,
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74 initially S000. The third column of the Parser Stack, which shows the
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75 token seen at that state, is initially blank. The Rule Stack will
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76 likewise be at level 0, state 000. The active pane of the Grammar
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77 Trace will be the Allowable Input pane, ready for you to choose a
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78 token.
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79 <BR>
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80
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81 <H3> Using Grammar Trace </H3>
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82
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83 At any stage, the Parser Stack pane represents a parse
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84 in progress. It shows the sequence of tokens that have
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85 been input so far and the states in which they were
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86 seen. When a production is complete and the grammar rule
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87 is reduced, the tokens that make up the rule are removed
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88 from the stack and replaced by the token on the left
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89 side of the production. The Rule Stack pane shows you all
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90 the grammar rules that are currently active
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91 at any level in the stack.
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92 <P>
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93
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94 To explore your grammar, choose a token from the Allowable Input
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95 pane. This pane shows the tokens allowable at the current state of the
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96 grammar, and the actions that result when the tokens are chosen.
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97 The Action field for each token shows whether it
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98 would cause a shift or a reduction, and the new state or the rule
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99 reduced. It is blank if the parser action is a compound action.
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100
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101 <P>
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102 Select a token by double-clicking it with the left mouse button or by
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103 positioning the cursor bar on the token and pressing Enter.
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104 Then the Parser Stack and Rule
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105 Stack will be modified to reflect the input choice you made. Note
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106 that the panes in the Grammar Trace window are synched with each
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107 other and also with your syntax file window if it is on-screen. The
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108 Rule Stack is particularly useful for seeing the relationship between
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109 the Parser Stack contents and your grammar.
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110
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111 <P>
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112 You may now continue stepping through your grammar. At any time, as an
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113 alternative to choosing tokens in the Allowable Input pane, you may
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114 type text in the combo box at the bottom of the Grammar Trace
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115 window and either press Enter or select the Proceed button to parse
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116 the text. The Single Step button will accept the combo box input one
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117 step at a time if the combo box is active, or the highlighted token
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118 if Allowable Input is active.
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119
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120 <P> You can back up the parse by
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121 moving the cursor bar in the Parser Stack window to the desired level
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122 and double-clicking the highlighted token in Allowable Input. You can
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123 reset the trace to the beginning with the Reset button.
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124
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125 <P>
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126 If you are using semantically determined productions, a Reduction
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127 Choices pane will appear to the left of the Rule Stack when it is
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128 time to reduce such a production. Select the desired reduction token
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129 from the pane before continuing with the parse.
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130
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131 <P>
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132 All Grammar Trace activity updates the trace coverage counts.
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133 <P>
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134
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135 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
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136 WIDTH=1010 HEIGHT=2 >
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137 <P>
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138 <IMG ALIGN="right" SRC="images/pslrb6d.gif" ALT="Parsifal Software"
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139 WIDTH=181 HEIGHT=25>
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140 <BR CLEAR="right">
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141
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142 <P>
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143 Back to <A HREF="index.html">Index</A>
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144 <P>
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145 <ADDRESS><FONT SIZE="-1">
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146 AnaGram parser generator - documentation<BR>
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147 Grammar Trace<BR>
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148 Copyright &copy; 1993-1999, Parsifal Software. <BR>
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149 All Rights Reserved.<BR>
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150 </FONT></ADDRESS>
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151
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152 </BODY>
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153 </HTML>
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154
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155