pt_peg_export_container(3)



pt::peg::export::container(3tcl) Parser Tools pt::peg::export::container(3tcl)

______________________________________________________________________________

NAME
       pt::peg::export::container - PEG Export Plugin. Write CONTAINER format

SYNOPSIS
       package require Tcl  8.5

       package require pt::peg::export::container  ?1?

       package require pt::peg::to::container

       export serial configuration

______________________________________________________________________________

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.  This document is the entrypoint to the whole system the
       current package is a part of.

       This package implements the parsing expression  grammar  export  plugin
       for the generation of CONTAINER markup.

       It  resides in the Export section of the Core Layer of Parser Tools and
       is intended to be used by pt::peg::export, the export manager,  sitting
       between it and the corresponding core conversion functionality provided
       by pt::peg::to::container.

       IMAGE: arch_core_eplugins

       While the direct use of this package with a regular interpreter is pos-
       sible, this is strongly disrecommended and requires a number of contor-
       tions to provide the expected environment.  The proper way to use  this
       functionality depends on the situation:

       [1]    In  an  untrusted  environment  the proper access is through the
              package pt::peg::export and the export manager objects  it  pro-
              vides.

       [2]    In   a  trusted  environment  however  simply  use  the  package
              pt::peg::to::container and access the core conversion  function-
              ality directly.

API
       The  API  provided  by  this package satisfies the specification of the
       Plugin API found in the Parser Tools Export API specification.

       export serial configuration
              This command takes the canonical serialization of a parsing  ex-
              pression grammar, as specified in section PEG serialization for-
              mat, and contained in serial, the configuration,  a  dictionary,
              and  generates  CONTAINER markup encoding the grammar.  The cre-
              ated string is then returned as the result of the command.

CONFIGURATION
       The CONTAINER export  plugin  recognizes  the  following  configuration
       variables and changes its behaviour as they specify.

       enum mode
              The  value of this configuration variable controls which methods
              of pt::peg instances the plugin will use to specify the grammar.
              There are two legal values

              bulk   In this mode the methods start, add, modes, and rules are
                     used to specify the grammar in a bulk manner, i.e.  as  a
                     set  of nonterminal symbols, and two dictionaries mapping
                     from the symbols to their semantic modes and parsing  ex-
                     pressions.

                     This mode is the default.

              incremental
                     In  this  mode the methods start, add, mode, and rule are
                     used to specify the grammar piecemal, with each nontermi-
                     nal having its own block of defining commands.

       string template
              If this configuration variable is set it is assumed to contain a
              string into which to put the generated code and other configura-
              tion  data.  The  various locations are expected to be specified
              with the following placeholders:

              @user@ To be replaced with the value of the configuration  vari-
                     able user.

              @format@
                     To be replaced with the the constant CONTAINER.

              @file@ To  be replaced with the value of the configuration vari-
                     able file.

              @name@ To be replaced with the value of the configuration  vari-
                     able name.

              @mode@ To  be replaced with the value of the configuration vari-
                     able mode.

              @code@ To be replaced with the generated code.

       If this configuration variable is not set, or empty,  then  the  plugin
       falls back to a standard template, which is defined as "@code@".

       Note  that  this plugin may ignore the standard configuration variables
       user, format, file, and their values, depending on the chosen template.

       The content of the standard configuration variable  name,  if  set,  is
       used  as  name of the grammar in the output. Otherwise the plugin falls
       back to the default name a_pe_grammar.

GRAMMAR CONTAINER
       The container format is another form of describing  parsing  expression
       grammars.  While  data in this format is executable it does not consti-
       tute a parser for the grammar. It always has to be used in  conjunction
       with the package pt::peg::interp, a grammar interpreter.

       The  format  represents grammars by a snit::type, i.e. class, whose in-
       stances are API-compatible to the instances of  the  pt::peg::container
       package, and which are preloaded with the grammar in question.

       It has no direct formal specification beyond what was said above.

   EXAMPLE
       Assuming the following PEG for simple mathematical expressions

              PEG calculator (Expression)
                  Digit      <- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9'       ;
                  Sign       <- '-' / '+'                                     ;
                  Number     <- Sign? Digit+                                  ;
                  Expression <- Term (AddOp Term)*                            ;
                  MulOp      <- '*' / '/'                                     ;
                  Term       <- Factor (MulOp Factor)*                        ;
                  AddOp      <- '+'/'-'                                       ;
                  Factor     <- '(' Expression ')' / Number                   ;
              END;

       one possible CONTAINER serialization for it is

              snit::type a_pe_grammar {
                  constructor {} {
                      install myg using pt::peg::container ${selfns}::G
                      $myg start {n Expression}
                      $myg add   AddOp Digit Expression Factor MulOp Number Sign Term
                      $myg modes {
                          AddOp      value
                          Digit      value
                          Expression value
                          Factor     value
                          MulOp      value
                          Number     value
                          Sign       value
                          Term       value
                      }
                      $myg rules {
                          AddOp      {/ {t -} {t +}}
                          Digit      {/ {t 0} {t 1} {t 2} {t 3} {t 4} {t 5} {t 6} {t 7} {t 8} {t 9}}
                          Expression {/ {x {t \50} {n Expression} {t \51}} {x {n Factor} {* {x {n MulOp} {n Factor}}}}}
                          Factor     {x {n Term} {* {x {n AddOp} {n Term}}}}
                          MulOp      {/ {t *} {t /}}
                          Number     {x {? {n Sign}} {+ {n Digit}}}
                          Sign       {/ {t -} {t +}}
                          Term       {n Number}
                      }
                      return
                  }

                  component myg
                  delegate method * to myg
              }

PEG SERIALIZATION FORMAT
       Here  we specify the format used by the Parser Tools to serialize Pars-
       ing Expression Grammars as immutable values for transport,  comparison,
       etc.

       We  distinguish  between regular and canonical serializations.  While a
       PEG may have more than one regular serialization only  exactly  one  of
       them will be canonical.

       regular serialization

              [1]    The serialization of any PEG is a nested Tcl dictionary.

              [2]    This dictionary holds a single key, pt::grammar::peg, and
                     its value. This value holds the contents of the grammar.

              [3]    The contents of the grammar are a Tcl dictionary  holding
                     the  set  of nonterminal symbols and the starting expres-
                     sion. The relevant keys and their values are

                     rules  The value is a Tcl dictionary whose keys  are  the
                            names  of  the  nonterminal  symbols  known to the
                            grammar.

                            [1]    Each  nonterminal  symbol  may  occur  only
                                   once.

                            [2]    The empty string is not a legal nonterminal
                                   symbol.

                            [3]    The value for each symbol is a Tcl  dictio-
                                   nary  itself.  The  relevant keys and their
                                   values in this dictionary are

                                   is     The value is  the  serialization  of
                                          the  parsing  expression  describing
                                          the symbols sentennial structure, as
                                          specified  in the section PE serial-
                                          ization format.

                                   mode   The value can be one of three values
                                          specifying  how a parser should han-
                                          dle the semantic value  produced  by
                                          the symbol.

                                          value  The  semantic  value  of  the
                                                 nonterminal symbol is an  ab-
                                                 stract syntax tree consisting
                                                 of a single node node for the
                                                 nonterminal itself, which has
                                                 the  ASTs  of  the   symbol's
                                                 right  hand side as its chil-
                                                 dren.

                                          leaf   The  semantic  value  of  the
                                                 nonterminal  symbol is an ab-
                                                 stract syntax tree consisting
                                                 of a single node node for the
                                                 nonterminal,   without    any
                                                 children.  Any ASTs generated
                                                 by the  symbol's  right  hand
                                                 side are discarded.

                                          void   The nonterminal has no seman-
                                                 tic value. Any ASTs generated
                                                 by  the  symbol's  right hand
                                                 side are discarded (as well).

                     start  The value is the serialization of the start  pars-
                            ing expression of the grammar, as specified in the
                            section PE serialization format.

              [4]    The terminal symbols of the grammar are specified implic-
                     itly as the set of all terminal symbols used in the start
                     expression and on the RHS of the grammar rules.

       canonical serialization
              The canonical serialization of a grammar has the format as spec-
              ified  in the previous item, and then additionally satisfies the
              constraints below, which make it unique among all  the  possible
              serializations of this grammar.

              [1]    The  keys  found  in  all the nested Tcl dictionaries are
                     sorted in ascending dictionary  order,  as  generated  by
                     Tcl's builtin command lsort -increasing -dict.

              [2]    The  string  representation of the value is the canonical
                     representation of a Tcl dictionary. I.e. it does not con-
                     tain superfluous whitespace.

   EXAMPLE
       Assuming the following PEG for simple mathematical expressions

              PEG calculator (Expression)
                  Digit      <- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9'       ;
                  Sign       <- '-' / '+'                                     ;
                  Number     <- Sign? Digit+                                  ;
                  Expression <- Term (AddOp Term)*                            ;
                  MulOp      <- '*' / '/'                                     ;
                  Term       <- Factor (MulOp Factor)*                        ;
                  AddOp      <- '+'/'-'                                       ;
                  Factor     <- '(' Expression ')' / Number                   ;
              END;

       then its canonical serialization (except for whitespace) is

              pt::grammar::peg {
                  rules {
                      AddOp      {is {/ {t -} {t +}}                                                                mode value}
                      Digit      {is {/ {t 0} {t 1} {t 2} {t 3} {t 4} {t 5} {t 6} {t 7} {t 8} {t 9}}                mode value}
                      Expression {is {x {n Term} {* {x {n AddOp} {n Term}}}}                                        mode value}
                      Factor     {is {/ {x {t (} {n Expression} {t )}} {n Number}}                                  mode value}
                      MulOp      {is {/ {t *} {t /}}                                                                mode value}
                      Number     {is {x {? {n Sign}} {+ {n Digit}}}                                                 mode value}
                      Sign       {is {/ {t -} {t +}}                                                                mode value}
                      Term       {is {x {n Factor} {* {x {n MulOp} {n Factor}}}}                                    mode value}
                  }
                  start {n Expression}
              }

PE SERIALIZATION FORMAT
       Here  we specify the format used by the Parser Tools to serialize Pars-
       ing Expressions as immutable values for transport, comparison, etc.

       We distinguish between regular and canonical serializations.   While  a
       parsing  expression  may  have more than one regular serialization only
       exactly one of them will be canonical.

       Regular serialization

              Atomic Parsing Expressions

                     [1]    The string epsilon is an  atomic  parsing  expres-
                            sion. It matches the empty string.

                     [2]    The string dot is an atomic parsing expression. It
                            matches any character.

                     [3]    The string alnum is an atomic parsing  expression.
                            It  matches  any Unicode alphabet or digit charac-
                            ter. This is a custom extension of  PEs  based  on
                            Tcl's builtin command string is.

                     [4]    The  string alpha is an atomic parsing expression.
                            It matches any Unicode alphabet character. This is
                            a  custom  extension of PEs based on Tcl's builtin
                            command string is.

                     [5]    The string ascii is an atomic parsing  expression.
                            It matches any Unicode character below U0080. This
                            is a  custom  extension  of  PEs  based  on  Tcl's
                            builtin command string is.

                     [6]    The  string  control  is an atomic parsing expres-
                            sion. It matches any  Unicode  control  character.
                            This  is  a custom extension of PEs based on Tcl's
                            builtin command string is.

                     [7]    The string digit is an atomic parsing  expression.
                            It  matches any Unicode digit character. Note that
                            this includes characters  outside  of  the  [0..9]
                            range.  This is a custom extension of PEs based on
                            Tcl's builtin command string is.

                     [8]    The string graph is an atomic parsing  expression.
                            It  matches any Unicode printing character, except
                            for space. This is a custom extension of PEs based
                            on Tcl's builtin command string is.

                     [9]    The  string lower is an atomic parsing expression.
                            It matches any Unicode lower-case alphabet charac-
                            ter.  This  is  a custom extension of PEs based on
                            Tcl's builtin command string is.

                     [10]   The string print is an atomic parsing  expression.
                            It matches any Unicode printing character, includ-
                            ing space. This is a custom extension of PEs based
                            on Tcl's builtin command string is.

                     [11]   The  string punct is an atomic parsing expression.
                            It matches any Unicode punctuation character. This
                            is  a  custom  extension  of  PEs  based  on Tcl's
                            builtin command string is.

                     [12]   The string space is an atomic parsing  expression.
                            It  matches any Unicode space character. This is a
                            custom extension of PEs  based  on  Tcl's  builtin
                            command string is.

                     [13]   The  string upper is an atomic parsing expression.
                            It matches any Unicode upper-case alphabet charac-
                            ter.  This  is  a custom extension of PEs based on
                            Tcl's builtin command string is.

                     [14]   The string wordchar is an atomic  parsing  expres-
                            sion.  It matches any Unicode word character. This
                            is any alphanumeric character (see alnum), and any
                            connector  punctuation  characters  (e.g.   under-
                            score). This is a custom extension of PEs based on
                            Tcl's builtin command string is.

                     [15]   The string xdigit is an atomic parsing expression.
                            It matches any hexadecimal digit  character.  This
                            is  a  custom  extension  of  PEs  based  on Tcl's
                            builtin command string is.

                     [16]   The string ddigit is an atomic parsing expression.
                            It  matches any decimal digit character. This is a
                            custom extension of PEs  based  on  Tcl's  builtin
                            command regexp.

                     [17]   The expression [list t x] is an atomic parsing ex-
                            pression. It matches the terminal string x.

                     [18]   The expression [list n A] is an atomic parsing ex-
                            pression. It matches the nonterminal A.

              Combined Parsing Expressions

                     [1]    For  parsing expressions e1, e2, ... the result of
                            [list / e1 e2 ... ] is  a  parsing  expression  as
                            well.  This is the ordered choice, aka prioritized
                            choice.

                     [2]    For parsing expressions e1, e2, ... the result  of
                            [list  x  e1  e2  ... ] is a parsing expression as
                            well.  This is the sequence.

                     [3]    For a parsing expression e the result of  [list  *
                            e]  is  a parsing expression as well.  This is the
                            kleene closure, describing zero  or  more  repeti-
                            tions.

                     [4]    For  a  parsing expression e the result of [list +
                            e] is a parsing expression as well.  This  is  the
                            positive  kleene  closure,  describing one or more
                            repetitions.

                     [5]    For a parsing expression e the result of  [list  &
                            e]  is  a parsing expression as well.  This is the
                            and lookahead predicate.

                     [6]    For a parsing expression e the result of  [list  !
                            e]  is  a parsing expression as well.  This is the
                            not lookahead predicate.

                     [7]    For a parsing expression e the result of  [list  ?
                            e]  is  a parsing expression as well.  This is the
                            optional input.

       Canonical serialization
              The canonical serialization of a parsing expression has the for-
              mat  as  specified  in  the previous item, and then additionally
              satisfies the constraints below, which make it unique among  all
              the possible serializations of this parsing expression.

              [1]    The  string  representation of the value is the canonical
                     representation of a pure Tcl list. I.e. it does not  con-
                     tain superfluous whitespace.

              [2]    Terminals  are not encoded as ranges (where start and end
                     of the range are identical).

   EXAMPLE
       Assuming the parsing expression shown on the  right-hand  side  of  the
       rule

                  Expression <- Term (AddOp Term)*

       then its canonical serialization (except for whitespace) is

                  {x {n Term} {* {x {n AddOp} {n Term}}}}

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 out-
       put 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
       CONTAINER,  EBNF, LL(k), PEG, TDPL, context-free languages, export, ex-
       pression, grammar, matching, parser, parsing  expression,  parsing  ex-
       pression grammar, plugin, push down automaton, recursive descent, seri-
       alization, state, top-down parsing languages, transducer

CATEGORY
       Parsing and Grammars

COPYRIGHT
       Copyright (c) 2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>

tcllib                                 1      pt::peg::export::container(3tcl)

Man(1) output converted with man2html
list of all man pages