NAME
page - Parser Generator
SYNOPSIS
page ?options...? ?input ?output??
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DESCRIPTION
The application described by this document, page, is actually not just
a parser generator, as the name implies, but a generic tool for the
execution of arbitrary transformations on texts.
Its genericity comes through the use of plugins for reading,
transforming, and writing data, and the predefined set of plugins
provided by Tcllib is for the generation of memoizing recursive descent
parsers (aka packrat parsers) from grammar specifications (Parsing
Expression Grammars).
page is written on top of the package page::pluginmgr, wrapping its
functionality into a command line based application. All the other
page::* packages are plugin and/or supporting packages for the
generation of parsers. The parsers themselves are based on the packages
grammar::peg, grammar::peg::interp, and grammar::mengine.
COMMAND LINE
page ?options...? ?input ?output??
This is general form for calling page. The application will read
the contents of the file input, process them under the control
of the specified options, and then write the result to the file
output.
If input is the string - the data to process will be read from
stdin instead of a file. Analogously the result will be written
to stdout instead of a file if output is the string -. A missing
output or input specification causes the application to assume
-.
The detailed specifications of the recognized options are
provided in section OPTIONS.
path input (in)
This argument specifies the path to the file to be
processed by the application, or -. The last value causes
the application to read the text from stdin. Otherwise it
has to exist, and be readable. If the argument is missing
- is assumed.
path output (in)
This argument specifies where to write the generated
text. It can be the path to a file, or -. The last value
causes the application to write the generated documented
to stdout.
If the file output does not exist then [file dirname
$output] has to exist and must be a writable directory,
as the application will create the fileto write to.
If the argument is missing - is assumed.
OPERATION
... reading ... transforming ... writing - plugins - pipeline ...
OPTIONS
This section describes all the options available to the user of the
application. Options are always processed in order. I.e. of both --help
and --version are specified the option encountered first has
precedence.
Unknown options specified before any of the options -rd, -wr, or -tr
will cause processing to abort with an error. Unknown options coming in
between these options, or after the last of them are assumed to always
take a single argument and are associated with the last plugin option
coming before them. They will be checked after all the relevant
plugins, and thus the options they understand, are known. I.e. such
unknown options cause error if and only if the plugin option they are
associated with does not understand them, and was not superceded by a
plugin option coming after.
Default options are used if and only if the command line did not
contain any options at all. They will set the application up as a PEG-
based parser generator. The exact list of options is
-c peg
And now the recognized options and their arguments, if they have any:
--help
-h
-? When one of these options is found on the command line all
arguments coming before or after are ignored. The application
will print a short description of the recognized options and
exit.
--version
-V When one of these options is found on the command line all
arguments coming before or after are ignored. The application
will print its own revision and exit.
-P This option signals the application to activate visual feedback
while reading the input.
-T This option signals the application to collect statistics while
reading the input and to print them after reading has completed,
before processing started.
-D This option signals the application to activate logging in the
Safe base, for the debugging of problems with plugins.
-r parser
-rd parser
--reader parser
These options specify the plugin the application has to use for
reading the input. If the options are used multiple times the
last one will be used.
-w generator
-wr generator
--writer generator
These options specify the plugin the application has to use for
generating and writing the final output. If the options are used
multiple times the last one will be used.
-t process
-tr process
--transform process
These options specify a plugin to run on the input. In contrast
to readers and writers each use will not supersede previous
uses, but add each chosen plugin to a list of transformations,
either at the front, or the end, per the last seen use of either
option -p or -a. The initial default is to append the new
transformations.
-a
--append
These options signal the application that all following
transformations should be added at the end of the list of
transformations.
-p
--prepend
These options signal the application that all following
transformations should be added at the beginning of the list of
transformations.
--reset
This option signals the application to clear the list of
transformations. This is necessary to wipe out the default
transformations used.
-c file
--configuration file
This option causes the application to load a configuration file
and/or plugin. This is a plugin which in essence provides a pre-
defined set of commandline options. They are processed exactly
as if they have been specified in place of the option and its
arguments. This means that unknown options found at the
beginning of the configuration file are associated with the last
plugin, even if that plugin was specified before the
configuration file itself. Conversely, unknown options coming
after the configuration file can be associated with a plugin
specified in the file.
If the argument is a file which cannot be loaded as a plugin the
application will assume that its contents are a list of options
and their arguments, separated by space, tabs, and newlines.
Options and argumentes containing spaces can be quoted via
double-quotes (") and quotes (’). The quote character can be
specified within in a quoted string by doubling it. Newlines in
a quoted string are accepted as is.
PLUGINS
page makes use of four different types of plugins, namely: readers,
writers, transformations, and configurations. Here we provide only a
basic introduction on how to use them from page. The exact APIs
provided to and expected from the plugins can be found in the
documentation for page::pluginmgr, for those who wish to write their
own plugins.
Plugins are specified as arguments to the options -r, -w, -t, -c, and
their equivalent longer forms. See the section OPTIONS for reference.
Each such argument will be first treated as the name of a file and this
file is loaded as the plugin. If however there is no file with that
name, then it will be translated into the name of a package, and this
package is then loaded. For each type of plugins the package management
searches not only the regular paths, but a set application- and type-
specific paths as well. Please see the section PLUGIN LOCATIONS for a
listing of all paths and their sources.
-c name
Configurations. The name of the package for the plugin name is
"page::config::name".
We have one predefined plugin:
peg It sets the application up as a parser generator
accepting parsing expression grammars and writing a
packrat parser in Tcl. The actual arguments it specifies
are:
--reset
--append
--reader peg
--transform reach
--transform use
--writer me
-r name
Readers. The name of the package for the plugin name is
"page::reader::name".
We have five predefined plugins:
peg Interprets the input as a parsing expression grammar
(PEG) and generates a tree representation for it. Both
the syntax of PEGs and the structure of the tree
representation are explained in their own manpages.
hb Interprets the input as Tcl code as generated by the
writer plugin hb and generates its tree representation.
ser Interprets the input as the serialization of a PEG, as
generated by the writer plugin ser, using the package
grammar::peg.
lemon Interprets the input as a grammar specification as
understood by Richard Hipp’s LEMON parser generator and
generates a tree representation for it. Both the input
syntax and the structure of the tree representation are
explained in their own manpages.
treeser
Interprets the input as the serialization of a
struct::tree. It is validated as such, but nothing else.
It is not assumed to be the tree representation of a
grammar.
-w name
Writers. The name of the package for the plugin name is
"page::writer::name".
We have eight predefined plugins:
identity
Simply writes the incoming data as it is, without making
any changes. This is good for inspecting the raw result
of a reader or transformation.
null Generates nothing, and ignores the incoming data
structure.
tree Assumes that the incoming data structure is a
struct::tree and generates an indented textual
representation of all nodes, their parental
relationships, and their attribute information.
peg Assumes that the incoming data structure is a tree
representation of a PEG or other other grammar and writes
it out as a PEG. The result is nicely formatted and
partially simplified (strings as sequences of
characters). A pretty printer in essence, but can also be
used to obtain a canonical representation of the input
grammar.
tpc Assumes that the incoming data structure is a tree
representation of a PEG or other other grammar and writes
out Tcl code defining a package which defines a
grammar::peg object containing the grammar when it is
loaded into an interpreter.
hb This is like the writer plugin tpc, but it writes only
the statements which define stat expression and grammar
rules. The code making the result a package is left out.
ser Assumes that the incoming data structure is a tree
representation of a PEG or other other grammar,
transforms it internally into a grammar::peg object and
writes out its serialization.
me Assumes that the incoming data structure is a tree
representation of a PEG or other other grammar and writes
out Tcl code defining a package which implements a
memoizing recursive descent parser based on the match
engine (ME) provided by the package grammar::mengine.
-t name
Transformers. The name of the package for the plugin name is
"page::transform::name".
We have two predefined plugins:
reach Assumes that the incoming data structure is a tree
representation of a PEG or other other grammar. It
determines which nonterminal symbols and rules are
reachable from start-symbol/expression. All nonterminal
symbols which were not reached are removed.
use Assumes that the incoming data structure is a tree
representation of a PEG or other other grammar. It
determines which nonterminal symbols and rules are able
to generate a finite sequences of terminal symbols (in
the sense for a Context Free Grammar). All nonterminal
symbols which were not deemed useful in this sense are
removed.
PLUGIN LOCATIONS
The application-specific paths searched by page either are, or come
from:
[1] The directory "~/.page/plugin"
[2] The environment variable PAGE_PLUGINS
[3] The registry entry
HKEY_LOCAL_MACHINE\SOFTWARE\PAGE\PLUGINS
[4] The registry entry HKEY_CURRENT_USER\SOFTWARE\PAGE\PLUGINS
The type-specific paths searched by page either are, or come from:
[1] The directory "~/.page/plugin/<TYPE>"
[2] The environment variable PAGE_<TYPE>_PLUGINS
[3] The registry entry
HKEY_LOCAL_MACHINE\SOFTWARE\PAGE\<TYPE>\PLUGINS
[4] The registry entry
HKEY_CURRENT_USER\SOFTWARE\PAGE\<TYPE>\PLUGINS
Where the placeholder <TYPE> is always one of the values below,
properly capitalized.
[1] reader
[2] writer
[3] transform
[4] config
The registry entries are specific to the Windows(tm) platform, all
other platforms will ignore them.
The contents of both environment variables and registry entries are
interpreted as a list of paths, with the elements separated by either
colon (Unix), or semicolon (Windows).
BUGS, IDEAS, FEEDBACK
This document, and the application it describes, will undoubtedly
contain bugs and other problems. Please report such in the category
page of the Tcllib SF Trackers
[http://sourceforge.net/tracker/?group_id=12883]. Please also report
any ideas for enhancements you may have for either application and/or
documentation.
SEE ALSO
page::pluginmgr
KEYWORDS
parser generator, text processing
CATEGORY
Page Parser Generator
COPYRIGHT
Copyright (c) 2005 Andreas Kupries <andreas_kupries@users.sourceforge.net>