'\"
'\" Generated from file 'dexec\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2004 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\" Copyright (c) 2007 Bogdan <rftghost@users\&.sourceforge\&.net>
'\"
.TH "grammar::fa::dexec" n 0\&.2 tcllib "Finite automaton operations and usage"
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.BS
.SH NAME
grammar::fa::dexec \- Execute deterministic finite automatons
.SH SYNOPSIS
package require \fBTcl  8\&.4\fR
.sp
package require \fBsnit \fR
.sp
package require \fBgrammar::fa::dexec  ?0\&.2?\fR
.sp
\fB::grammar::fa::dexec\fR \fIdaName\fR \fIfa\fR ?\fB-any\fR \fIany\fR? ?\fB-command\fR \fIcmdprefix\fR?
.sp
\fBdaName\fR \fIoption\fR ?\fIarg arg \&.\&.\&.\fR?
.sp
\fIdaName\fR \fBdestroy\fR
.sp
\fIdaName\fR \fBput\fR \fIsymbol\fR
.sp
\fIdaName\fR \fBreset\fR
.sp
\fIdaName\fR \fBstate\fR
.sp
\fIcmdprefix\fR \fBerror\fR \fIcode\fR \fImessage\fR
.sp
\fIcmdprefix\fR \fBfinal\fR \fIstateid\fR
.sp
\fIcmdprefix\fR \fBreset\fR
.sp
\fIcmdprefix\fR \fBstate\fR \fIstateid\fR
.sp
.BE
.SH DESCRIPTION
.PP
This package provides a class for executors constructed from
deterministic \fIfinite automatons\fR (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 \fBgrammar::fa\fR and \fBgrammar::fa::op\fR\&.
.PP
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 \fB-command\fR\&. 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\&.
.PP
\fISide note\fR:
The acceptor objects provided by \fBgrammar::fa::dacceptor\fR
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)\&.
.PP
.SH API
The package exports the API described here\&.
.TP
\fB::grammar::fa::dexec\fR \fIdaName\fR \fIfa\fR ?\fB-any\fR \fIany\fR? ?\fB-command\fR \fIcmdprefix\fR?
Creates a new deterministic executor with an associated global Tcl
command whose name is \fIdaName\fR\&. This command may be used to invoke
various operations on the executor\&. It has the following general form:
.RS
.TP
\fBdaName\fR \fIoption\fR ?\fIarg arg \&.\&.\&.\fR?
\fIOption\fR and the \fIarg\fRs determine the exact behavior of the
command\&. See section \fBEXECUTOR METHODS\fR for more
explanations\&.
.sp
The executor will be based on the deterministic finite automaton
stored in the object \fIfa\fR\&. It will keep a copy of the relevant
data of the FA in its own storage, in a form easy to use for its
purposes\&. This also means that changes made to the \fIfa\fR after the
construction of the executor \fIwill not\fR influence the executor\&.
.sp
If \fIany\fR has been specified, then the executor will convert all
symbols in the input which are unknown to the base FA to that symbol
before proceeding with the processing\&.
.RE
.PP
.SH "EXECUTOR METHODS"
.PP
All executors provide the following methods for their manipulation:
.TP
\fIdaName\fR \fBdestroy\fR
Destroys the automaton, including its storage space and associated
command\&.
.TP
\fIdaName\fR \fBput\fR \fIsymbol\fR
Takes the current state of the executor and the \fIsymbol\fR and
performs the appropriate state transition\&. Reports any errors
encountered via the command callback, as well as entering a final
state of the underlying FA\&.
.sp
When an error is reported all further invokations of \fBput\fR will
do nothing, until the error condition has been cleared via an
invokation of method \fBreset\fR\&.
.TP
\fIdaName\fR \fBreset\fR
Unconditionally sets the executor into the start state of the
underlying FA\&. This also clears any error condition  \fBput\fR may
have encountered\&.
.TP
\fIdaName\fR \fBstate\fR
Returns the current state of the underlying FA\&. This allow for
introspection without the need to pass data from the callback command\&.
.PP
.SH "EXECUTOR CALLBACK"
The callback command \fIcmdprefix\fR given to an executor via the
option \fB-command\fR will be executed by the object at the global
level, using the syntax described below\&. Note that \fIcmdprefix\fR 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\&.
.TP
\fIcmdprefix\fR \fBerror\fR \fIcode\fR \fImessage\fR
The executor has encountered an error, and \fImessage\fR contains a
human-readable text explaining the nature of the problem\&.
The \fIcode\fR on the other hand is a fixed machine-readable text\&.
The following error codes can be generated by executor objects\&.
.RS
.TP
\fBBADSYM\fR
An unknown symbol was found in the input\&. This can happen if and only
if no \fB-any\fR symbol was specified\&.
.TP
\fBBADTRANS\fR
The underlying FA has no transition for the current combination of
input symbol and state\&. In other words, the executor was not able to
compute a new state for this combination\&.
.RE
.TP
\fIcmdprefix\fR \fBfinal\fR \fIstateid\fR
The executor has entered the final state \fIstateid\fR\&.
.TP
\fIcmdprefix\fR \fBreset\fR
The executor was reset\&.
.TP
\fIcmdprefix\fR \fBstate\fR \fIstateid\fR
The FA changed state due to a transition\&. \fIstateid\fR is the new state\&.
.PP
.PP
.SH EXAMPLES
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems\&.
Please report such in the category \fIgrammar_fa\fR of the
\fITcllib Trackers\fR [http://core\&.tcl\&.tk/tcllib/reportlist]\&.
Please also report any ideas for enhancements you may have for either
package and/or documentation\&.
.SH KEYWORDS
automaton, execution, finite automaton, grammar, parsing, regular expression, regular grammar, regular languages, running, state, transducer
.SH CATEGORY
Grammars and finite automata
.SH COPYRIGHT
.nf
Copyright (c) 2004 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
Copyright (c) 2007 Bogdan <rftghost@users\&.sourceforge\&.net>

.fi