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Import AnaGram (near-)release tree into Mercurial.
author David A. Holland
date Sat, 22 Dec 2007 17:52:45 -0500
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1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
2 <HTML>
3 <HEAD>
4 <TITLE>AnaGram's Grammar Trace Facility</TITLE>
5
6 </HEAD>
7
8 <BODY BGCOLOR="#ffffff" BACKGROUND="tilbl6h.gif"
9 TEXT="#000000" LINK="#0033CC"
10 VLINK="#CC0033" ALINK="#CC0099">
11
12 <P>
13 <IMG ALIGN="right" SRC="images/agrsl6c.gif" ALT="AnaGram"
14 WIDTH=124 HEIGHT=30>
15 <BR CLEAR="RIGHT">
16 </P>
17
18 <P>
19 Back to <A HREF="index.html">Index</A>
20 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
21 WIDTH=1010 HEIGHT=2 >
22
23 <H2>AnaGram's Grammar Trace</H2>
24 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
25 WIDTH=1010 HEIGHT=2 >
26
27 <P>
28
29 The Grammar Trace facility lets you examine the workings of your
30 parser in detail, <ITALIC>interactively</ITALIC>. You can use Grammar Trace even
31 <ITALIC>before</ITALIC> you
32 write any code to attach to the rules of your grammar, and before actually
33 building a parser. If you have a test file available, you may prefer to use <A
34 HREF="ftrace.html"><STRONG>File Trace</STRONG></A>.
35 <P>
36 Using the various options associated with this trace
37 you can set up a representation of the parser state stack and parser
38 state as they might appear in the course of execution of your
39 parser. You can then examine the allowable input tokens and the
40 changes to the state and the state stack caused by any input tokens you
41 choose.
42
43 <IMG ALIGN="right" SRC="gramtr6g.gif" ALT="sample Grammar Trace window"
44 WIDTH=489 HEIGHT=338 VSPACE=8 HSPACE=8 >
45
46
47 <P>
48 AnaGram now provides a combo box where you can enter input characters
49 for a Grammar Trace, in addition to choosing tokens. This means you can
50 run a Grammar Trace like a <A
51 HREF="ftrace.html">File Trace</A> where the test file is replaced
52 by the combo box characters you type. This is a very convenient way
53 to check out your grammar.
54 </P>
55
56 <BR>
57
58 <H3> Starting Grammar Traces:</H3>
59
60 A Grammar Trace can be selected from either the Action Menu or the
61 Control Panel toolbar once your grammar has been analyzed. There are
62 also prebuilt grammar traces like the Conflict Trace and the
63 Auxiliary Trace, which can be selected from the Auxiliary Windows
64 popup menu for certain AnaGram windows or panes.
65 <P>
66 Like File Trace, a Grammar Trace presents three principal panes. These
67 are a Parser Stack pane on the left, an Allowable Input pane on the
68 right, and a Rule Stack pane at the bottom.
69 <P>
70 Initially, the Parser Stack will consist of a single line, which
71 represents the initial configuration of your parser. The first column
72 will show zero, which is the value of the parser stack
73 index. The second column will show the state number of the parser,
74 initially S000. The third column of the Parser Stack, which shows the
75 token seen at that state, is initially blank. The Rule Stack will
76 likewise be at level 0, state 000. The active pane of the Grammar
77 Trace will be the Allowable Input pane, ready for you to choose a
78 token.
79 <BR>
80
81 <H3> Using Grammar Trace </H3>
82
83 At any stage, the Parser Stack pane represents a parse
84 in progress. It shows the sequence of tokens that have
85 been input so far and the states in which they were
86 seen. When a production is complete and the grammar rule
87 is reduced, the tokens that make up the rule are removed
88 from the stack and replaced by the token on the left
89 side of the production. The Rule Stack pane shows you all
90 the grammar rules that are currently active
91 at any level in the stack.
92 <P>
93
94 To explore your grammar, choose a token from the Allowable Input
95 pane. This pane shows the tokens allowable at the current state of the
96 grammar, and the actions that result when the tokens are chosen.
97 The Action field for each token shows whether it
98 would cause a shift or a reduction, and the new state or the rule
99 reduced. It is blank if the parser action is a compound action.
100
101 <P>
102 Select a token by double-clicking it with the left mouse button or by
103 positioning the cursor bar on the token and pressing Enter.
104 Then the Parser Stack and Rule
105 Stack will be modified to reflect the input choice you made. Note
106 that the panes in the Grammar Trace window are synched with each
107 other and also with your syntax file window if it is on-screen. The
108 Rule Stack is particularly useful for seeing the relationship between
109 the Parser Stack contents and your grammar.
110
111 <P>
112 You may now continue stepping through your grammar. At any time, as an
113 alternative to choosing tokens in the Allowable Input pane, you may
114 type text in the combo box at the bottom of the Grammar Trace
115 window and either press Enter or select the Proceed button to parse
116 the text. The Single Step button will accept the combo box input one
117 step at a time if the combo box is active, or the highlighted token
118 if Allowable Input is active.
119
120 <P> You can back up the parse by
121 moving the cursor bar in the Parser Stack window to the desired level
122 and double-clicking the highlighted token in Allowable Input. You can
123 reset the trace to the beginning with the Reset button.
124
125 <P>
126 If you are using semantically determined productions, a Reduction
127 Choices pane will appear to the left of the Rule Stack when it is
128 time to reduce such a production. Select the desired reduction token
129 from the pane before continuing with the parse.
130
131 <P>
132 All Grammar Trace activity updates the trace coverage counts.
133 <P>
134
135 <IMG ALIGN="bottom" SRC="images/rbline6j.gif" ALT="----------------------"
136 WIDTH=1010 HEIGHT=2 >
137 <P>
138 <IMG ALIGN="right" SRC="images/pslrb6d.gif" ALT="Parsifal Software"
139 WIDTH=181 HEIGHT=25>
140 <BR CLEAR="right">
141
142 <P>
143 Back to <A HREF="index.html">Index</A>
144 <P>
145 <ADDRESS><FONT SIZE="-1">
146 AnaGram parser generator - documentation<BR>
147 Grammar Trace<BR>
148 Copyright &copy; 1993-1999, Parsifal Software. <BR>
149 All Rights Reserved.<BR>
150 </FONT></ADDRESS>
151
152 </BODY>
153 </HTML>
154
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