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EuroTcl/OpenACS 11 - 12 JULY 2024, VIENNA

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grammar::fa::dexec - Execute deterministic finite automatons

Table Of Contents


package require Tcl 8.5 9
package require snit
package require grammar::fa::dexec ?0.3?

::grammar::fa::dexec daName fa ?-any any? ?-command cmdprefix?
daName option ?arg arg ...?
daName destroy
daName put symbol
daName reset
daName state
cmdprefix error code message
cmdprefix final stateid
cmdprefix reset
cmdprefix state stateid


This package provides a class for executors constructed from deterministic finite automatons (DFA). Executors are objects which are given a string of symbols in a piecemal fashion, perform state transitions and report back when they enter a final state, or find an error in the input. For the actual creation of the DFAs the executors are based on we have the packages grammar::fa and grammar::fa::op.

The objects follow a push model. Symbols are pushed into the executor, and when something important happens, i.e. error occurs, a state transition, or a final state is entered this will be reported via the callback specified via the option -command. Note that conversion of this into a pull model where the environment retrieves messages from the object and the object uses a callback to ask for more symbols is a trivial thing.

Side note: The acceptor objects provided by grammar::fa::dacceptor could have been implemented on top of the executors provided here, but were not, to get a bit more performance (we avoid a number of method calls and the time required for their dispatch).


The package exports the API described here.


All executors provide the following methods for their manipulation:


The callback command cmdprefix given to an executor via the option -command will be executed by the object at the global level, using the syntax described below. Note that cmdprefix is not simply the name of a command, but a full command prefix. In other words it may contain additional fixed argument words beyond the command word.


Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category grammar_fa of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.

When proposing code changes, please provide unified diffs, i.e the output of diff -u.

Note further that attachments are strongly preferred over inlined patches. Attachments can be made by going to the Edit form of the ticket immediately after its creation, and then using the left-most button in the secondary navigation bar.


automaton, execution, finite automaton, grammar, parsing, regular expression, regular grammar, regular languages, running, state, transducer


Grammars and finite automata


Copyright © 2004 Andreas Kupries
Copyright © 2007 Bogdan