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annotate doc/misc/html/gtrace.html @ 7:57b2cc9b87f7

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Use memcpy instead of strncpy when we know the length anyway. Modern gcc seems to think it knows how to detect misuse of strncpy, but it's wrong (in fact: very, very wrong) and the path of least resistance is to not try to fight with it.
author David A. Holland
date Mon, 30 May 2022 23:47:52 -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