'\"
'\" Generated from file 'me_cpu\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2005-2006 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\"
.TH "grammar::me::cpu" n 0\&.2 tcllib "Grammar operations and usage"
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.BS
.SH NAME
grammar::me::cpu \- Virtual machine implementation II for parsing token streams
.SH SYNOPSIS
package require \fBTcl  8\&.4\fR
.sp
package require \fBgrammar::me::cpu  ?0\&.2?\fR
.sp
\fB::grammar::me::cpu\fR \fImeName\fR \fImatchcode\fR
.sp
\fBmeName\fR \fBoption\fR ?\fIarg arg \&.\&.\&.\fR?
.sp
\fImeName\fR \fBlc\fR \fIlocation\fR
.sp
\fImeName\fR \fBtok\fR ?\fIfrom\fR ?\fIto\fR??
.sp
\fImeName\fR \fBpc\fR \fIstate\fR
.sp
\fImeName\fR \fBiseof\fR \fIstate\fR
.sp
\fImeName\fR \fBat\fR \fIstate\fR
.sp
\fImeName\fR \fBcc\fR \fIstate\fR
.sp
\fImeName\fR \fBsv\fR
.sp
\fImeName\fR \fBok\fR
.sp
\fImeName\fR \fBerror\fR
.sp
\fImeName\fR \fBlstk\fR \fIstate\fR
.sp
\fImeName\fR \fBastk\fR \fIstate\fR
.sp
\fImeName\fR \fBmstk\fR \fIstate\fR
.sp
\fImeName\fR \fBestk\fR \fIstate\fR
.sp
\fImeName\fR \fBrstk\fR \fIstate\fR
.sp
\fImeName\fR \fBnc\fR \fIstate\fR
.sp
\fImeName\fR \fBast\fR
.sp
\fImeName\fR \fBhalted\fR
.sp
\fImeName\fR \fBcode\fR
.sp
\fImeName\fR \fBeof\fR
.sp
\fImeName\fR \fBput\fR \fItok\fR \fIlex\fR \fIline\fR \fIcol\fR
.sp
\fImeName\fR \fBputstring\fR \fIstring\fR \fIlvar\fR \fIcvar\fR
.sp
\fImeName\fR \fBrun\fR ?\fIn\fR?
.sp
\fImeName\fR \fBpull\fR \fInextcmd\fR
.sp
\fImeName\fR \fBreset\fR
.sp
\fImeName\fR \fBdestroy\fR
.sp
.BE
.SH DESCRIPTION
.PP
This package provides an implementation of the ME virtual machine\&.
Please go and read the document \fBgrammar::me_intro\fR first if
you do not know what a ME virtual machine is\&.
.PP
This implementation provides an object-based API and the machines are
not truly tied to Tcl\&. A C implementation of the same API is quite
possible\&.
.PP
Internally the package actually uses the value-based machine
manipulation commands as provided by the package
\fBgrammar::me::cpu::core\fR to perform its duties\&.
.SH API
.SS "CLASS API"
The package directly provides only a single command for the
construction of ME virtual machines\&.
.TP
\fB::grammar::me::cpu\fR \fImeName\fR \fImatchcode\fR
The command creates a new ME machine object with an associated global
Tcl command whose name is \fImeName\fR\&. This command may be used to
invoke various operations on the machine\&.
It has the following general form:
.RS
.TP
\fBmeName\fR \fBoption\fR ?\fIarg arg \&.\&.\&.\fR?
\fIOption\fR and the \fIarg\fRs determine the exact behavior of the
command\&.
.RE
.sp
The argument \fImatchcode\fR contains the match instructions the
machine has to execute while parsing the input stream\&. Please read
section \fBMATCH CODE REPRESENTATION\fR of the
documentation for the package \fBgrammar::me::cpu::core\fR for
the specification of the structure of this value\&.
.sp
The \fItokmap\fR argument taken by the implementation provided by the
package \fBgrammar::me::tcl\fR is here hidden inside of the match
instructions and therefore not needed\&.
.PP
.PP
.SS "OBJECT API"
All ME virtual machine objects created by the class command specified
in section \fBCLASS API\fR support the methods listed below\&.
.PP
The machines provided by this package provide methods for operation in
both push- and pull-styles\&. Push-style means that tokens are pushed
into the machine state when they arrive, triggering further execution
until they are consumed\&. In other words, this allows the machine to be
suspended and resumed at will and an arbitrary number of times, the
quasi-parallel operation of several machines, and the operation as
part of the event loop\&.
.TP
\fImeName\fR \fBlc\fR \fIlocation\fR
This method converts the location of a token given as offset in the
input stream into the associated line number and column index\&. The
result of the command is a 2-element list containing the two values,
in the order mentioned in the previous sentence\&.
This allows higher levels to convert the location information found in
the error status and the generated AST into more human readable data\&.
.sp
\fINote\fR that the command is not able to convert locations which
have not been reached by the machine yet\&. In other words, if the
machine has read 7 tokens the command is able to convert the offsets
\fB0\fR to \fB6\fR, but nothing beyond that\&. This also shows that
it is not possible to convert offsets which refer to locations before
the beginning of the stream\&.
.TP
\fImeName\fR \fBtok\fR ?\fIfrom\fR ?\fIto\fR??
This method returns a Tcl list containing the part of the input stream
between the locations \fIfrom\fR and \fIto\fR (both inclusive)\&. If
\fIto\fR is not specified it will default to the value of \fIfrom\fR\&.
If \fIfrom\fR is not specified either the whole input stream is returned\&.
.sp
Each element of the returned list is a list of four elements, the
token, its associated lexeme, line number, and column index, in this
order\&.
This command places the same restrictions on its location arguments as
the method \fBlc\fR\&.
.TP
\fImeName\fR \fBpc\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the current value of the stored program counter\&.
.TP
\fImeName\fR \fBiseof\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the current value of the stored eof flag\&.
.TP
\fImeName\fR \fBat\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the current location in the input stream\&.
.TP
\fImeName\fR \fBcc\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the current token\&.
.TP
\fImeName\fR \fBsv\fR
This command returns the current semantic value \fISV\fR stored in
the machine\&. This is an abstract syntax tree as specified in the
document \fBgrammar::me_ast\fR, section \fBAST VALUES\fR\&.
.TP
\fImeName\fR \fBok\fR
This method returns the current match status \fIOK\fR\&.
.TP
\fImeName\fR \fBerror\fR
This method returns the current error status \fIER\fR\&.
.TP
\fImeName\fR \fBlstk\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the location stack\&.
.TP
\fImeName\fR \fBastk\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the AST stack\&.
.TP
\fImeName\fR \fBmstk\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the AST marker stack\&.
.TP
\fImeName\fR \fBestk\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the error stack\&.
.TP
\fImeName\fR \fBrstk\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the subroutine return stack\&.
.TP
\fImeName\fR \fBnc\fR \fIstate\fR
This method takes the state value of a ME virtual machine and returns
the nonterminal match cache as a dictionary\&.
.TP
\fImeName\fR \fBast\fR
This method returns the current top entry of the AST stack \fIAS\fR\&.
This is an abstract syntax tree as specified in the document
\fBgrammar::me_ast\fR, section \fBAST VALUES\fR\&.
.TP
\fImeName\fR \fBhalted\fR
This method returns a boolean value telling the caller whether the
engine has halted execution or not\&. Halt means that no further
matching is possible, and the information retrieved via the other
method is final\&. Attempts to \fBrun\fR the engine will be ignored,
until a \fBreset\fR is made\&.
.TP
\fImeName\fR \fBcode\fR
This method returns the \fIcode\fR information used to construct the
object\&. In other words, the match program executed by the machine\&.
.TP
\fImeName\fR \fBeof\fR
This method adds an end of file marker to the end of the input stream\&.
This signals the machine that the current contents of the input queue
are the final parts of the input and nothing will come after\&. Attempts
to put more characters into the queue will fail\&.
.TP
\fImeName\fR \fBput\fR \fItok\fR \fIlex\fR \fIline\fR \fIcol\fR
This method adds the token \fItok\fR to the end of the input stream,
with associated lexeme data \fIlex\fR and \fIline\fR/\fIcol\fRumn
information\&.
.TP
\fImeName\fR \fBputstring\fR \fIstring\fR \fIlvar\fR \fIcvar\fR
This method adds each individual character in the \fIstring\fR as a
token to the end of the input stream, from first to last\&. The lexemes
will be empty and the line/col information is computed based on the
characters encountered and the data in the variables \fIlvar\fR and
\fIcvar\fR\&.
.TP
\fImeName\fR \fBrun\fR ?\fIn\fR?
This methods causes the engine to execute match instructions until
either
.RS
.IP \(bu
\fIn\fR instructions have been executed, or
.IP \(bu
a halt instruction was executed, or
.IP \(bu
the input queue is empty and the code is asking for more tokens to
process\&.
.RE
.sp
If no limit \fIn\fR was set only the last two conditions are checked
for\&.
.TP
\fImeName\fR \fBpull\fR \fInextcmd\fR
This method implements pull-style operation of the machine\&. It causes
it to execute match instructions until either a halt instruction is
reached, or the command prefix
\fInextcmd\fR ceases to deliver more tokens\&.
.sp
The command prefix \fInextcmd\fR represents the input stream of
characters and is invoked by the machine whenever the a new character
from the stream is required\&. The instruction for handling this is
\fIict_advance\fR\&.
The callback has to return either the empty list, or a list of 4
elements containing the token, its lexeme attribute, and its location
as line number and column index, in this order\&.
The empty list is the signal that the end of the input stream has been
reached\&. The lexeme attribute is stored in the terminal cache, but
otherwise not used by the machine\&.
.sp
The end of the input stream for this method does not imply that method
\fBeof\fR is called for the machine as a whole\&. By avoiding this
and still asking for an explicit call of the method it is possible to
mix push- and pull-style operation during the lifetime of the machine\&.
.TP
\fImeName\fR \fBreset\fR
This method resets the machine to its initial state, discarding any
state it may have\&.
.TP
\fImeName\fR \fBdestroy\fR
This method deletes the object and releases all resurces it claimed\&.
.PP
.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_me\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\&.
.PP
When proposing code changes, please provide \fIunified diffs\fR,
i\&.e the output of \fBdiff -u\fR\&.
.PP
Note further that \fIattachments\fR are strongly preferred over
inlined patches\&. Attachments can be made by going to the \fBEdit\fR
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar\&.
.SH KEYWORDS
grammar, parsing, virtual machine
.SH CATEGORY
Grammars and finite automata
.SH COPYRIGHT
.nf
Copyright (c) 2005-2006 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>

.fi