Tcl Library Source Code

'\"
'\" Generated from file 'pt_parse_peg\&.man' by tcllib/doctools with format 'nroff'
'\" Copyright (c) 2009 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>
'\"
.TH "pt_parse_peg" i 1 tcllib "Parser Tools"
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.BS
.SH NAME
pt_parse_peg \- Parser Tools PEG Parser
.SH SYNOPSIS
package require \fBTcl  8\&.5\fR
.sp
package require \fBpt::parse::peg  1\fR
.sp
\fBpt::parse::peg\fR ?\fIobjectName\fR?
.sp
\fIobjectName\fR \fBdestroy\fR
.sp
\fIobjectName\fR \fBparse\fR \fIchan\fR
.sp
\fIobjectName\fR \fBparset\fR \fItext\fR
.sp
.BE
.SH DESCRIPTION
.PP
Are you lost ?
Do you have trouble understanding this document ?
In that case please read the overview provided by the
\fIIntroduction to Parser Tools\fR\&. This document is the
entrypoint to the whole system the current package is a part of\&.
.PP
This package provides a class whose instances are parsers for parsing
expression grammars in textual form\&.
.SH "CLASS API"
.TP
\fBpt::parse::peg\fR ?\fIobjectName\fR?
The class command constructs parser instances, i\&.e\&. objects\&. The
result of the command is the fully-qualified name of the instance
command\&.
.sp
If no \fIobjectName\fR is specified the class will generate and use an
automatic name\&. If the \fIobjectName\fR was specified, but is not
fully qualified the command will be created in the current namespace\&.
.PP
.SH "INSTANCES API"
All parser instances provide at least the methods shown below:
.TP
\fIobjectName\fR \fBdestroy\fR
This method destroys the parser instance, releasing all claimed memory
and other resources, and deleting the instance command\&.
.sp
The result of the command is the empty string\&.
.TP
\fIobjectName\fR \fBparse\fR \fIchan\fR
This method runs the parser using the contents of \fIchan\fR as input
(starting at the current location in the channel), until parsing is
not possible anymore, either because parsing has completed, or run
into a syntax error\&.
.sp
Note here that the Parser Tools are based on Tcl 8\&.5+\&. In other words,
the channel argument is not restricted to files, sockets, etc\&. We have
the full power of \fIreflected channels\fR available\&.
.sp
It should also be noted that the parser pulls the characters from the
input stream as it needs them\&. If a parser created by this package has
to be operated in a push aka event-driven manner it will be necessary
to go to Tcl 8\&.6+ and use the \fBcoroutine::auto\fR to wrap it
into a coroutine where \fBread\fR is properly changed for
push-operation\&.
.sp
Upon successful completion the command returns an abstract syntax tree
as its result\&.
This AST is in the form specified in section
\fBAST serialization format\fR\&.
As a plain nested Tcl-list it can then be processed with any Tcl
commands the user likes, doing transformations, semantic checks, etc\&.
To help in this the package \fBpt::ast\fR provides a set of
convenience commands for validation of the tree's basic structure,
printing it for debugging, and walking it either from the bottom up,
or top down\&.
.sp
When encountering a syntax error the command will throw an error instead\&.
This error will be a 4-element Tcl-list, containing, in the order
listed below:
.RS
.IP [1]
The string \fBpt::rde\fR identifying it as parser runtime error\&.
.IP [2]
The location of the parse error, as character offset from the
beginning of the parsed input\&.
.IP [3]
The location of parse error, now as a 2-element list containing
line-number and column in the line\&.
.IP [4]
A set of atomic parsing expressions indicating encoding the characters
and/or nonterminal symbols the parser expected to see at the location
of the parse error, but did not get\&.
For the specification of atomic parsing expressions please see the
section \fBPE serialization format\fR\&.
.RE
.TP
\fIobjectName\fR \fBparset\fR \fItext\fR
This method runs the parser using the string in \fItext\fR as input\&.
In all other ways it behaves like the method \fBparse\fR, shown
above\&.
.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 \fIpt\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
EBNF, LL(k), PEG, TDPL, context-free languages, expression, grammar, matching, parser, parsing expression, parsing expression grammar, push down automaton, recursive descent, state, top-down parsing languages, transducer
.SH CATEGORY
Parsing and Grammars
.SH COPYRIGHT
.nf
Copyright (c) 2009 Andreas Kupries <andreas_kupries@users\&.sourceforge\&.net>

.fi