[//000000001]: # (pt::rde \- Parser Tools) [//000000002]: # (Generated from file 'pt\_rdengine\.man' by tcllib/doctools with format 'markdown') [//000000003]: # (Copyright © 2009 Andreas Kupries ) [//000000004]: # (pt::rde\(n\) 1\.1 tcllib "Parser Tools")
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# NAME pt::rde \- Parsing Runtime Support, PARAM based # Table Of Contents - [Table Of Contents](#toc) - [Synopsis](#synopsis) - [Description](#section1) - [Class API](#subsection1) - [Object API](#subsection2) - [Bugs, Ideas, Feedback](#section2) - [Keywords](#keywords) - [Category](#category) - [Copyright](#copyright) # SYNOPSIS package require Tcl 8\.5 package require pt::rde ?1\.1? package require snit package require struct::stack 1\.5 package require pt::ast 1\.1 [__::pt::rde__ *objectName*](#1) [*objectName* __destroy__](#2) [*objectName* __reset__ *chan*](#3) [*objectName* __complete__](#4) [*objectName* __chan__](#5) [*objectName* __line__](#6) [*objectName* __column__](#7) [*objectName* __current__](#8) [*objectName* __location__](#9) [*objectName* __locations__](#10) [*objectName* __ok__](#11) [*objectName* __value__](#12) [*objectName* __error__](#13) [*objectName* __errors__](#14) [*objectName* __tokens__ ?*from* ?*to*??](#15) [*objectName* __symbols__](#16) [*objectName* __known__](#17) [*objectName* __reducible__](#18) [*objectName* __asts__](#19) [*objectName* __ast__](#20) [*objectName* __position__ *loc*](#21) [*objectName* __i\_input\_next__ *msg*](#22) [*objectName* __i\_test\_alnum__](#23) [*objectName* __i\_test\_alpha__](#24) [*objectName* __i\_test\_ascii__](#25) [*objectName* __i\_test\_char__ *char*](#26) [*objectName* __i\_test\_ddigit__](#27) [*objectName* __i\_test\_digit__](#28) [*objectName* __i\_test\_graph__](#29) [*objectName* __i\_test\_lower__](#30) [*objectName* __i\_test\_print__](#31) [*objectName* __i\_test\_punct__](#32) [*objectName* __i\_test\_range__ *chars* *chare*](#33) [*objectName* __i\_test\_space__](#34) [*objectName* __i\_test\_upper__](#35) [*objectName* __i\_test\_wordchar__](#36) [*objectName* __i\_test\_xdigit__](#37) [*objectName* __i\_error\_clear__](#38) [*objectName* __i\_error\_push__](#39) [*objectName* __i\_error\_pop\_merge__](#40) [*objectName* __i\_error\_nonterminal__ *symbol*](#41) [*objectName* __i\_status\_ok__](#42) [*objectName* __i\_status\_fail__](#43) [*objectName* __i\_status\_negate__](#44) [*objectName* __i\_loc\_push__](#45) [*objectName* __i\_loc\_pop\_discard__](#46) [*objectName* __i\_loc\_pop\_rewind__](#47) [*objectName* __i:ok\_loc\_pop\_rewind__](#48) [*objectName* __i\_loc\_pop\_rewind/discard__](#49) [*objectName* __i\_symbol\_restore__ *symbol*](#50) [*objectName* __i\_symbol\_save__ *symbol*](#51) [*objectName* __i\_value\_clear__](#52) [*objectName* __i\_value\_clear/leaf__](#53) [*objectName* __i\_value\_clear/reduce__](#54) [*objectName* __i:ok\_ast\_value\_push__](#55) [*objectName* __i\_ast\_push__](#56) [*objectName* __i\_ast\_pop\_rewind__](#57) [*objectName* __i:fail\_ast\_pop\_rewind__](#58) [*objectName* __i\_ast\_pop\_rewind/discard__](#59) [*objectName* __i\_ast\_pop\_discard__](#60) [*objectName* __i\_ast\_pop\_discard/rewind__](#61) [*objectName* __i:ok\_continue__](#62) [*objectName* __i:fail\_continue__](#63) [*objectName* __i:fail\_return__](#64) [*objectName* __i:ok\_return__](#65) [*objectName* __si:void\_state\_push__](#66) [*objectName* __si:void2\_state\_push__](#67) [*objectName* __si:value\_state\_push__](#68) [*objectName* __si:void\_state\_merge__](#69) [*objectName* __si:void\_state\_merge\_ok__](#70) [*objectName* __si:value\_state\_merge__](#71) [*objectName* __si:value\_notahead\_start__](#72) [*objectName* __si:void\_notahead\_exit__](#73) [*objectName* __si:value\_notahead\_exit__](#74) [*objectName* __si:kleene\_abort__](#75) [*objectName* __si:kleene\_close__](#76) [*objectName* __si:voidvoid\_branch__](#77) [*objectName* __si:voidvalue\_branch__](#78) [*objectName* __si:valuevoid\_branch__](#79) [*objectName* __si:valuevalue\_branch__](#80) [*objectName* __si:voidvoid\_part__](#81) [*objectName* __si:voidvalue\_part__](#82) [*objectName* __si:valuevalue\_part__](#83) [*objectName* __si:value\_symbol\_start__ *symbol*](#84) [*objectName* __si:value\_void\_symbol\_start__ *symbol*](#85) [*objectName* __si:void\_symbol\_start__ *symbol*](#86) [*objectName* __si:void\_void\_symbol\_start__ *symbol*](#87) [*objectName* __si:reduce\_symbol\_end__ *symbol*](#88) [*objectName* __si:void\_leaf\_symbol\_end__ *symbol*](#89) [*objectName* __si:value\_leaf\_symbol\_end__ *symbol*](#90) [*objectName* __si:value\_clear\_symbol\_end__ *symbol*](#91) [*objectName* __si:void\_clear\_symbol\_end__ *symbol*](#92) [*objectName* __si:next\_char__ *tok*](#93) [*objectName* __si:next\_range__ *toks* *toke*](#94) [*objectName* __si:next\_alnum__](#95) [*objectName* __si:next\_alpha__](#96) [*objectName* __si:next\_ascii__](#97) [*objectName* __si:next\_ddigit__](#98) [*objectName* __si:next\_digit__](#99) [*objectName* __si:next\_graph__](#100) [*objectName* __si:next\_lower__](#101) [*objectName* __si:next\_print__](#102) [*objectName* __si:next\_punct__](#103) [*objectName* __si:next\_space__](#104) [*objectName* __si:next\_upper__](#105) [*objectName* __si:next\_wordchar__](#106) [*objectName* __si:next\_xdigit__](#107) # DESCRIPTION Are you lost ? Do you have trouble understanding this document ? In that case please read the overview provided by the *[Introduction to Parser Tools](pt\_introduction\.md)*\. This document is the entrypoint to the whole system the current package is a part of\. This package provides a class whose instances provide the runtime support for recursive descent parsers with backtracking, as is needed for the execution of, for example, parsing expression grammars\. It implements the *[PackRat Machine Specification](pt\_param\.md)*, as such that document is *required* reading to understand both this manpage, and the package itself\. The description below does make numerous shorthand references to the PARAM's instructions and the various parts of its architectural state\. The package resides in the Execution section of the Core Layer of Parser Tools\. ![](\.\./\.\./\.\./\.\./image/arch\_core\_transform\.png) Note: This package not only has the standard Tcl implementation, but also an accelerator, i\.e\. a C implementation, based on Critcl\. ## Class API The package exports the API described here\. - __::pt::rde__ *objectName* The command creates a new runtime object for a recursive descent parser with backtracking and returns the fully qualified name of the object command as its result\. The API of this object command is described in the section [Object API](#subsection2)\. It may be used to invoke various operations on the object\. ## Object API All objects created by this package provide the following 63 methods for the manipulation and querying of their state, which is, in essence the architectural state of a PARAM\. First some general methods and the state accessors\. - *objectName* __destroy__ This method destroys the object, releasing all claimed memory, and deleting the associated object command\. - *objectName* __reset__ *chan* This method resets the state of the runtme to its defaults, preparing it for the parsing of the character in the channel *chan*, which becomes IN\. 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 *reflected channels* available\. 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 __[coroutine::auto](\.\./coroutine/coro\_auto\.md)__ to wrap it into a coroutine where __[read](\.\./\.\./\.\./\.\./index\.md\#read)__ is properly changed for push\-operation\. - *objectName* __complete__ This method completes parsing, either returning the AST made from the elements of ARS, or throwing an error containing the current ER\. - *objectName* __chan__ This method returns the handle of the channel which is IN\. - *objectName* __line__ This method returns the line number for the position IN is currently at\. Note that this may not match with the line number for CL, due to backtracking\. - *objectName* __column__ This method returns the column for the position IN is currently at\. Note that this may not match with the column for CL, due to backtracking\. - *objectName* __current__ This method returns CC\. - *objectName* __location__ This method returns CL\. - *objectName* __locations__ This method returns the LS\. The topmost entry of the stack will be the first element of the returned list\. - *objectName* __ok__ This method returns ST\. - *objectName* __value__ This method returns SV\. - *objectName* __error__ This method returns ER\. This is either the empty string for an empty ER, or a list of 2 elements, the location the error is for, and a set of messages which specify which symbols were expected at the location\. The messages are encoded as one of the possible atomic parsing expressions \(special operators, terminal, range, and nonterminal operator\)\. - *objectName* __errors__ This method returns ES\. The topmost entry of the stack will be the first element of the returned list\. Each entry is encoded as described for __error__\. - *objectName* __tokens__ ?*from* ?*to*?? This method returns the part of TC for the range of locations of IN starting at *from* and ending at *to*\. If *to* is not specified it is taken as identical to *from*\. If neither argument is specified the whole of TC is returned\. Each token in the returned list is a list of three elements itself, containing the character at the location, and the associated line and column numbers, in this order\. - *objectName* __symbols__ This method returns a dictionary containing NC\. Keys are two\-element lists containing nonterminal symbol and location, in this order\. The values are 4\-tuples containing CL, ST, ER, and SV, in this order\. ER is encoded as specified for the method __error__\. - *objectName* __known__ This method returns a list containing the keys of SC\. They are encoded in the same manner as is done by method __symbols__\. - *objectName* __reducible__ This method returns ARS\. The topmost entry of the stack will be the first element of the returned list - *objectName* __asts__ This method returns AS\. The topmost entry of the stack will be the first element of the returned list - *objectName* __ast__ This is a convenience method returning the topmost element of ARS\. - *objectName* __position__ *loc* This method returns the line and column numbers for the specified location of IN, assuming that this location has already been reached during the parsing process\. The following methods implement all PARAM instructions\. They all have the prefix "i\_"\. The control flow is mainly provided by Tcl's builtin commands, like __if__, __while__, etc\., plus a few guarded variants of PARAM instructions and Tcl commands\.\. That means that these instruction variants will do nothing if their guard condition is not fulfilled\. They can be recognized by the prefix "i:ok\_" and "i:fail\_", which denote the value ST has to have for the instruction to execute\. The instructions are listed in the same order they occur in the *[PackRat Machine Specification](pt\_param\.md)*, with the guard variants listed after their regular implementation, if any, or in their place\. - *objectName* __i\_input\_next__ *msg* This method implements the PARAM instruction __input\_next__\. - *objectName* __i\_test\_alnum__ This method implements the PARAM instruction __test\_alnum__\. - *objectName* __i\_test\_alpha__ This method implements the PARAM instruction __test\_alpha__\. - *objectName* __i\_test\_ascii__ This method implements the PARAM instruction __test\_ascii__\. - *objectName* __i\_test\_char__ *char* This method implements the PARAM instruction __test\_char__\. - *objectName* __i\_test\_ddigit__ This method implements the PARAM instruction __test\_ddigit__\. - *objectName* __i\_test\_digit__ This method implements the PARAM instruction __test\_digit__\. - *objectName* __i\_test\_graph__ This method implements the PARAM instruction __test\_graph__\. - *objectName* __i\_test\_lower__ This method implements the PARAM instruction __test\_lower__\. - *objectName* __i\_test\_print__ This method implements the PARAM instruction __test\_print__\. - *objectName* __i\_test\_punct__ This method implements the PARAM instruction __test\_punct__\. - *objectName* __i\_test\_range__ *chars* *chare* This method implements the PARAM instruction __test\_range__\. - *objectName* __i\_test\_space__ This method implements the PARAM instruction __test\_space__\. - *objectName* __i\_test\_upper__ This method implements the PARAM instruction __test\_upper__\. - *objectName* __i\_test\_wordchar__ This method implements the PARAM instruction __test\_wordchar__\. - *objectName* __i\_test\_xdigit__ This method implements the PARAM instruction __test\_xdigit__\. - *objectName* __i\_error\_clear__ This method implements the PARAM instruction __error\_clear__\. - *objectName* __i\_error\_push__ This method implements the PARAM instruction __error\_push__\. - *objectName* __i\_error\_pop\_merge__ This method implements the PARAM instruction __error\_pop\_merge__\. - *objectName* __i\_error\_nonterminal__ *symbol* This method implements the PARAM instruction __error\_nonterminal__\. - *objectName* __i\_status\_ok__ This method implements the PARAM instruction __status\_ok__\. - *objectName* __i\_status\_fail__ This method implements the PARAM instruction __status\_fail__\. - *objectName* __i\_status\_negate__ This method implements the PARAM instruction __status\_negate__\. - *objectName* __i\_loc\_push__ This method implements the PARAM instruction __loc\_push__\. - *objectName* __i\_loc\_pop\_discard__ This method implements the PARAM instruction __loc\_pop\_discard__\. - *objectName* __i\_loc\_pop\_rewind__ This method implements the PARAM instruction __loc\_pop\_rewind__\. - *objectName* __i:ok\_loc\_pop\_rewind__ This guarded method, a variant of __i\_loc\_pop\_rewind__, executes only for "ST == ok"\. - *objectName* __i\_loc\_pop\_rewind/discard__ This method is a convenient combination of control flow and the two PARAM instructions __loc\_pop\_rewind__ and __loc\_pop\_discard__\. The former is executed for "ST == fail", the latter for "ST == ok"\. - *objectName* __i\_symbol\_restore__ *symbol* This method implements the PARAM instruction __symbol\_restore__\. The boolean result of the check is returned as the result of the method and can be used with standard Tcl control flow commands\. - *objectName* __i\_symbol\_save__ *symbol* This method implements the PARAM instruction __symbol\_save__\. - *objectName* __i\_value\_clear__ This method implements the PARAM instruction __value\_clear__\. - *objectName* __i\_value\_clear/leaf__ This method is a convenient combination of control flow and the two PARAM instructions __value\_clear__ and __value\_leaf__\. The former is executed for "ST == fail", the latter for "ST == ok"\. - *objectName* __i\_value\_clear/reduce__ This method is a convenient combination of control flow and the two PARAM instructions __value\_clear__ and __value\_reduce__\. The former is executed for "ST == fail", the latter for "ST == ok"\. - *objectName* __i:ok\_ast\_value\_push__ This method implements a guarded variant of the the PARAM instruction __ast\_value\_push__, which executes only for "ST == ok"\. - *objectName* __i\_ast\_push__ This method implements the PARAM instruction __ast\_push__\. - *objectName* __i\_ast\_pop\_rewind__ This method implements the PARAM instruction __ast\_pop\_rewind__\. - *objectName* __i:fail\_ast\_pop\_rewind__ This guarded method, a variant of __i\_ast\_pop\_rewind__, executes only for "ST == fail"\. - *objectName* __i\_ast\_pop\_rewind/discard__ This method is a convenient combination of control flow and the two PARAM instructions __ast\_pop\_rewind__ and __ast\_pop\_discard__\. The former is executed for "ST == fail", the latter for "ST == ok"\. - *objectName* __i\_ast\_pop\_discard__ This method implements the PARAM instruction __ast\_pop\_discard__\. - *objectName* __i\_ast\_pop\_discard/rewind__ This method is a convenient combination of control flow and the two PARAM instructions __ast\_pop\_discard__ and __ast\_pop\_rewind__\. The former is executed for "ST == fail", the latter for "ST == ok"\. - *objectName* __i:ok\_continue__ This guarded method executes only for "ST == ok"\. Then it aborts the current iteration of the innermost loop in the calling Tcl procedure\. - *objectName* __i:fail\_continue__ This guarded method executes only for "ST == fail"\. Then it aborts the current iteration of the innermost loop in the calling Tcl procedure\. - *objectName* __i:fail\_return__ This guarded method executes only for "ST == fail"\. Then it aborts the calling Tcl procedure\. - *objectName* __i:ok\_return__ This guarded method executes only for "ST == ok"\. Then it aborts the calling Tcl procedure\. The next set of methods are *super instructions*, meaning that each implements a longer sequence of instructions commonly used in parsers\. The combinated instructions of the previous set, i\.e\. those with names matching the pattern "i\_\*/\*", are actually super instructions as well, albeit with limited scope, handling 2 instructions with their control flow\. The upcoming set is much broader in scope, folding as much as six or more PARAM instructions into a single method call\. In this we can see the reasoning behind their use well: 1. By using less instructions the generated parsers become smaller, as the common parts are now truly part of the common runtime, and not explicitly written in the parser's code over and over again\. 1. Using less instructions additionally reduces the overhead associated with calls into the runtime, i\.e\. the cost of method dispatch and of setting up the variable context\. 1. Another effect of the super instructions is that their internals can be optimized as well, especially regarding control flow, and stack use, as the runtime internals are accessible to all instructions folded into the sequence\. - *objectName* __si:void\_state\_push__ This method combines i_loc_push i_error_clear i_error_push Parsers use it at the beginning of *void* sequences and choices with a *void* initial branch\. - *objectName* __si:void2\_state\_push__ This method combines i_loc_push i_error_clear i_error_push Parsers use it at the beginning of optional and repeated expressions\. - *objectName* __si:value\_state\_push__ This method combines i_ast_push i_loc_push i_error_clear i_error_push Parsers use it at the beginning of sequences generating an AST and choices with an initial branch generating an AST\. - *objectName* __si:void\_state\_merge__ This method combines i_error_pop_merge i_loc_pop_rewind/discard Parsers use it at the end of void sequences and choices whose last branch is void\. - *objectName* __si:void\_state\_merge\_ok__ This method combines i_error_pop_merge i_loc_pop_rewind/discard i_status_ok Parsers use it at the end of optional expressions - *objectName* __si:value\_state\_merge__ This method combines i_error_pop_merge i_ast_pop_rewind/discard i_loc_pop_rewind/discard Parsers use it at the end of sequences generating ASTs and choices whose last branch generates an AST - *objectName* __si:value\_notahead\_start__ This method combines i_loc_push i_ast_push Parsers use it at the beginning of negative lookahead predicates which generate ASTs\. - *objectName* __si:void\_notahead\_exit__ This method combines i_loc_pop_rewind i_status_negate Parsers use it at the end of void negative lookahead predicates\. - *objectName* __si:value\_notahead\_exit__ This method combines i_ast_pop_discard/rewind i_loc_pop_rewind i_status_negate Parsers use it at the end of negative lookahead predicates which generate ASTs\. - *objectName* __si:kleene\_abort__ This method combines i_loc_pop_rewind/discard i:fail_return Parsers use it to stop a positive repetition when its first, required, expression fails\. - *objectName* __si:kleene\_close__ This method combines i_error_pop_merge i_loc_pop_rewind/discard i:fail_status_ok i:fail_return Parsers use it at the end of repetitions\. - *objectName* __si:voidvoid\_branch__ This method combines i_error_pop_merge i:ok_loc_pop_discard i:ok_return i_loc_rewind i_error_push Parsers use it when transiting between branches of a choice when both are void\. - *objectName* __si:voidvalue\_branch__ This method combines i_error_pop_merge i:ok_loc_pop_discard i:ok_return i_ast_push i_loc_rewind i_error_push Parsers use it when transiting between branches of a choice when the failing branch is void, and the next to test generates an AST\. - *objectName* __si:valuevoid\_branch__ This method combines i_error_pop_merge i_ast_pop_rewind/discard i:ok_loc_pop_discard i:ok_return i_loc_rewind i_error_push Parsers use it when transiting between branches of a choice when the failing branch generates an AST, and the next to test is void\. - *objectName* __si:valuevalue\_branch__ This method combines i_error_pop_merge i_ast_pop_discard i:ok_loc_pop_discard i:ok_return i_ast_rewind i_loc_rewind i_error_push Parsers use it when transiting between branches of a choice when both generate ASTs\. - *objectName* __si:voidvoid\_part__ This method combines i_error_pop_merge i:fail_loc_pop_rewind i:fail_return i_error_push Parsers use it when transiting between parts of a sequence and both are void\. - *objectName* __si:voidvalue\_part__ This method combines i_error_pop_merge i:fail_loc_pop_rewind i:fail_return i_ast_push i_error_push Parsers use it when transiting between parts of a sequence and the sucessfully matched part is void, and after it an AST is generated\. - *objectName* __si:valuevalue\_part__ This method combines i_error_pop_merge i:fail_ast_pop_rewind i:fail_loc_pop_rewind i:fail_return i_error_push Parsers use it when transiting between parts of a sequence and both parts generate ASTs\. - *objectName* __si:value\_symbol\_start__ *symbol* This method combines if/found? i_symbol_restore $symbol i:found:ok_ast_value_push i:found_return i_loc_push i_ast_push Parsers use it at the beginning of a nonterminal symbol generating an AST, whose right\-hand side may have generated an AST as well\. - *objectName* __si:value\_void\_symbol\_start__ *symbol* This method combines if/found? i_symbol_restore $symbol i:found:ok_ast_value_push i:found_return i_loc_push i_ast_push Parsers use it at the beginning of a void nonterminal symbol whose right\-hand side may generate an AST\. - *objectName* __si:void\_symbol\_start__ *symbol* This method combines if/found? i_symbol_restore $symbol i:found_return i_loc_push i_ast_push Parsers use it at the beginning of a nonterminal symbol generating an AST whose right\-hand side is void\. - *objectName* __si:void\_void\_symbol\_start__ *symbol* This method combines if/found? i_symbol_restore $symbol i:found_return i_loc_push Parsers use it at the beginning of a void nonterminal symbol whose right\-hand side is void as well\. - *objectName* __si:reduce\_symbol\_end__ *symbol* This method combines i_value_clear/reduce $symbol i_symbol_save $symbol i_error_nonterminal $symbol i_ast_pop_rewind i_loc_pop_discard i:ok_ast_value_push Parsers use it at the end of a non\-terminal symbol generating an AST using the AST generated by the right\-hand side as child\. - *objectName* __si:void\_leaf\_symbol\_end__ *symbol* This method combines i_value_clear/leaf $symbol i_symbol_save $symbol i_error_nonterminal $symbol i_loc_pop_discard i:ok_ast_value_push Parsers use it at the end of a non\-terminal symbol generating an AST whose right\-hand side is void\. - *objectName* __si:value\_leaf\_symbol\_end__ *symbol* This method combines i_value_clear/leaf $symbol i_symbol_save $symbol i_error_nonterminal $symbol i_loc_pop_discard i_ast_pop_rewind i:ok_ast_value_push Parsers use it at the end of a non\-terminal symbol generating an AST discarding the AST generated by the right\-hand side\. - *objectName* __si:value\_clear\_symbol\_end__ *symbol* This method combines i_value_clear i_symbol_save $symbol i_error_nonterminal $symbol i_loc_pop_discard i_ast_pop_rewind Parsers use it at the end of a void non\-terminal symbol, discarding the AST generated by the right\-hand side\. - *objectName* __si:void\_clear\_symbol\_end__ *symbol* This method combines i_value_clear i_symbol_save $symbol i_error_nonterminal $symbol i_loc_pop_discard Parsers use it at the end of a void non\-terminal symbol with a void right\-hand side\. - *objectName* __si:next\_char__ *tok* - *objectName* __si:next\_range__ *toks* *toke* - *objectName* __si:next\_alnum__ - *objectName* __si:next\_alpha__ - *objectName* __si:next\_ascii__ - *objectName* __si:next\_ddigit__ - *objectName* __si:next\_digit__ - *objectName* __si:next\_graph__ - *objectName* __si:next\_lower__ - *objectName* __si:next\_print__ - *objectName* __si:next\_punct__ - *objectName* __si:next\_space__ - *objectName* __si:next\_upper__ - *objectName* __si:next\_wordchar__ - *objectName* __si:next\_xdigit__ These methods all combine i_input_next $msg i:fail_return with the appropriate __i\_test\_xxx__ instruction\. Parsers use them for handling atomic expressions\. # Bugs, Ideas, Feedback This document, and the package it describes, will undoubtedly contain bugs and other problems\. Please report such in the category *pt* of the [Tcllib Trackers](http://core\.tcl\.tk/tcllib/reportlist)\. 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\. # KEYWORDS [EBNF](\.\./\.\./\.\./\.\./index\.md\#ebnf), [LL\(k\)](\.\./\.\./\.\./\.\./index\.md\#ll\_k\_), [PEG](\.\./\.\./\.\./\.\./index\.md\#peg), [TDPL](\.\./\.\./\.\./\.\./index\.md\#tdpl), [context\-free languages](\.\./\.\./\.\./\.\./index\.md\#context\_free\_languages), [expression](\.\./\.\./\.\./\.\./index\.md\#expression), [grammar](\.\./\.\./\.\./\.\./index\.md\#grammar), [matching](\.\./\.\./\.\./\.\./index\.md\#matching), [parser](\.\./\.\./\.\./\.\./index\.md\#parser), [parsing expression](\.\./\.\./\.\./\.\./index\.md\#parsing\_expression), [parsing expression grammar](\.\./\.\./\.\./\.\./index\.md\#parsing\_expression\_grammar), [push down automaton](\.\./\.\./\.\./\.\./index\.md\#push\_down\_automaton), [recursive descent](\.\./\.\./\.\./\.\./index\.md\#recursive\_descent), [state](\.\./\.\./\.\./\.\./index\.md\#state), [top\-down parsing languages](\.\./\.\./\.\./\.\./index\.md\#top\_down\_parsing\_languages), [transducer](\.\./\.\./\.\./\.\./index\.md\#transducer) # CATEGORY Parsing and Grammars # COPYRIGHT Copyright © 2009 Andreas Kupries