1grammar::fa::dexec(n)Finite automaton operations and usagegrammar::fa::dexec(n)
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8 grammar::fa::dexec - Execute deterministic finite automatons
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11 package require Tcl 8.4
12 package require snit
14 package require grammar::fa::dexec ?0.2?
16 ::grammar::fa::dexec daName fa ?-any any? ?-command cmdprefix?
18 daName option ?arg arg ...?
20 daName destroy
22 daName put symbol
24 daName reset
26 daName state
28 cmdprefix error code message
30 cmdprefix final stateid
32 cmdprefix reset
34 cmdprefix state stateid
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38
40 This package provides a class for executors constructed from determin‐
41 istic finite automatons (DFA). Executors are objects which are given a
42 string of symbols in a piecemal fashion, perform state transitions and
43 report back when they enter a final state, or find an error in the
44 input. For the actual creation of the DFAs the executors are based on
45 we have the packages grammar::fa and grammar::fa::op.
46 The objects follow a push model. Symbols are pushed into the executor,
48 and when something important happens, i.e. error occurs, a state tran‐
49 sition, or a final state is entered this will be reported via the call‐
50 back specified via the option -command. Note that conversion of this
51 into a pull model where the environment retrieves messages from the
52 object and the object uses a callback to ask for more symbols is a
53 trivial thing.
54 Side note: The acceptor objects provided by grammar::fa::dacceptor
56 could have been implemented on top of the executors provided here, but
57 were not, to get a bit more performance (we avoid a number of method
58 calls and the time required for their dispatch).
59
61 The package exports the API described here.
62 ::grammar::fa::dexec daName fa ?-any any? ?-command cmdprefix?
64 Creates a new deterministic executor with an associated global
65 Tcl command whose name is daName. This command may be used to
66 invoke various operations on the executor. It has the following
67 general form:
68 daName option ?arg arg ...?
70 Option and the args determine the exact behavior of the
71 command. See section EXECUTOR METHODS for more explana‐
72 tions.
73 The executor will be based on the deterministic finite
75 automaton stored in the object fa. It will keep a copy of
76 the relevant data of the FA in its own storage, in a form
77 easy to use for its purposes. This also means that
78 changes made to the fa after the construction of the
79 executor will not influence the executor.
80 If any has been specified, then the executor will convert
82 all symbols in the input which are unknown to the base FA
83 to that symbol before proceeding with the processing.
84
86 All executors provide the following methods for their manipulation:
87 daName destroy
89 Destroys the automaton, including its storage space and associ‐
90 ated command.
91 daName put symbol
93 Takes the current state of the executor and the symbol and per‐
94 forms the appropriate state transition. Reports any errors
95 encountered via the command callback, as well as entering a
96 final state of the underlying FA.
97 When an error is reported all further invokations of put will do
99 nothing, until the error condition has been cleared via an
100 invokation of method reset.
101 daName reset
103 Unconditionally sets the executor into the start state of the
104 underlying FA. This also clears any error condition put may
105 have encountered.
106 daName state
108 Returns the current state of the underlying FA. This allow for
109 introspection without the need to pass data from the callback
110 command.
111
113 The callback command cmdprefix given to an executor via the option
114 -command will be executed by the object at the global level, using the
115 syntax described below. Note that cmdprefix is not simply the name of a
116 command, but a full command prefix. In other words it may contain addi‐
117 tional fixed argument words beyond the command word.
118 cmdprefix error code message
120 The executor has encountered an error, and message contains a
121 human-readable text explaining the nature of the problem. The
122 code on the other hand is a fixed machine-readable text. The
123 following error codes can be generated by executor objects.
124 BADSYM An unknown symbol was found in the input. This can happen
126 if and only if no -any symbol was specified.
127 BADTRANS
129 The underlying FA has no transition for the current com‐
130 bination of input symbol and state. In other words, the
131 executor was not able to compute a new state for this
132 combination.
133 cmdprefix final stateid
135 The executor has entered the final state stateid.
136 cmdprefix reset
138 The executor was reset.
139 cmdprefix state stateid
141 The FA changed state due to a transition. stateid is the new
142 state.
143
146 This document, and the package it describes, will undoubtedly contain
147 bugs and other problems. Please report such in the category grammar_fa
148 of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please
149 also report any ideas for enhancements you may have for either package
150 and/or documentation.
151 When proposing code changes, please provide unified diffs, i.e the out‐
153 put of diff -u.
154 Note further that attachments are strongly preferred over inlined
156 patches. Attachments can be made by going to the Edit form of the
157 ticket immediately after its creation, and then using the left-most
158 button in the secondary navigation bar.
159
161 automaton, execution, finite automaton, grammar, parsing, regular
162 expression, regular grammar, regular languages, running, state, trans‐
163 ducer
164
166 Grammars and finite automata
167
169 Copyright (c) 2004 Andreas Kupries <andreas_kupries@users.sourceforge.net>
170 Copyright (c) 2007 Bogdan <rftghost@users.sourceforge.net>
171tcllib 0.2 grammar::fa::dexec(n)