pt::peg::to::tclparam(n)

📦
version 2.0 · 2 versions
, in fedora 43, fedora 44, nixos 26.05, nixpkgs unstable

💖 NAME 💖

pt::peg::to::tclparam — PEG Conversion. Write TCLPARAM format. It's the Parser Tools girlie that turns your parsing expression grammars into TCLPARAM markup, and bestie, she is so good at her job. 🦋

✨ SYNOPSIS ✨

package require Tcl 8.5 9

package require pt::peg::to::tclparam ?1.0.4?

pt::peg::to::tclparam reset

pt::peg::to::tclparam configure

pt::peg::to::tclparam configure option

pt::peg::to::tclparam configure option value...

pt::peg::to::tclparam convert serial

🌸 DESCRIPTION 🌸

Okay so first thing — are you lost ? Are you having trouble understanding this document ? 😭 No shame, it happens. In that case please go read the overview provided by the Introduction to Parser Tools. That document is literally the entrypoint to the whole system this package is a part of. iykyk.

This package implements the converter from parsing expression grammars to TCLPARAM markup. Periodt.

It resides in the Export section of the Core Layer of Parser Tools, and you can use it two ways, bestie:

  • directly, with the other packages of this layer, or
  • indirectly, through the export manager provided by pt::peg::export. That route is intented for use in untrusted environments, and it goes through the corresponding export plugin pt::peg::export::tclparam, which sits between the converter and the export manager.

IMAGE: arch_core_eplugins

💅 API 💅

The API this package hands you satisfies the specification of the Converter API found in the Parser Tools Export API specification. No cap.

  • pt::peg::to::tclparam reset — This command resets the configuration of the package to its default settings. Fresh start energy. 🧼
  • pt::peg::to::tclparam configure — This command returns a dictionary containing the current configuration of the package. Like a lil mirror, showing you the whole config. 🪞
  • pt::peg::to::tclparam configure option — This command returns the current value of the specified configuration option of the package. For the set of legal options, please read the section Options. 👑
  • pt::peg::to::tclparam configure option value... — This command sets the given configuration options of the package, to the specified values. For the set of legal options, please read the section Options. You're in charge, bestie. ✨
  • pt::peg::to::tclparam convert serial — This command takes the canonical serialization of a parsing expression grammar, as specified in section PEG serialization format, and contained in serial, and generates TCLPARAM markup encoding the grammar, per the current package configuration. The created string is then returned as the result of the command. That's it, that's the main character. 🌟

🎀 OPTIONS 🎀

The converter to Tcl/PARAM markup recognizes the following configuration variables and changes its behaviour as they specify. So many knobs, and honestly? We love that for us.

  • -template string — The value of this configuration variable is a string into which to put the generated text and the other configuration settings. The various locations for user-data are expected to be specified with the placeholders listed below. The default value is "@code@".
    • @user@ — To be replaced with the value of the configuration variable -user.
    • @format@ — To be replaced with the the constant Tcl/PARAM.
    • @file@ — To be replaced with the value of the configuration variable -file.
    • @name@ — To be replaced with the value of the configuration variable -name.
    • @code@ — To be replaced with the generated Tcl code.

The following configuration variables are special, in that they will occur within the generated code, and are replaced there as well. 👀

  • @runtime@ — To be replaced with the value of the configuration variable runtime-command.
  • @self@ — To be replaced with the value of the configuration variable self-command.
  • @def@ — To be replaced with the value of the configuration variable proc-command.
  • @ns@ — To be replaced with the value of the configuration variable namespace.
  • @main@ — To be replaced with the value of the configuration variable main.
  • @prelude@ — To be replaced with the value of the configuration variable prelude.
  • -name string — The value of this configuration variable is the name of the grammar for which the conversion is run. The default value is a_pe_grammar.
  • -user string — The value of this configuration variable is the name of the user for which the conversion is run. The default value is unknown.
  • -file string — The value of this configuration variable is the name of the file or other entity from which the grammar came, for which the conversion is run. The default value is unknown.
  • -runtime-command string — A Tcl string representing the Tcl command or reference to it used to call PARAM instruction from parser procedures, per the chosen framework (template). The default value is the empty string.
  • -self-command string — A Tcl string representing the Tcl command or reference to it used to call the parser procedures (methods ...) from another parser procedure, per the chosen framework (template). The default value is the empty string.
  • -proc-command string — The name of the Tcl command used to define procedures (methods ...), per the chosen framework (template). The default value is proc.
  • -namespace string — The name of the namespace the parser procedures (methods, ...) shall reside in, including the trailing '::' needed to separate it from the actual procedure name. The default value is ::.
  • -main string — The name of the main procedure (method, ...) to be called by the chosen framework (template) to start parsing input. The default value is __main.
  • -prelude string — A snippet of code to be insert at the head of each generated parsing command. The default value is the empty string.
  • -indent integer — The number of characters to indent each line of the generated code by. The default value is 0.

While the high parameterizability of this converter, as shown by the multitude of options it supports, is an advantage to the advanced user, allowing her to customize the output of the converter as needed, a novice user will likely not see the forest for the trees. 🫠 Real. It's giving option overload, lowkey.

To help these latter users two adjunct packages are provided, each containing a canned configuration which will generate immediately useful full parsers. These are:

  • pt::tclparam::configuration::snit — Generated parsers are classes based on the snit package, i.e. snit::type's.
  • pt::tclparam::configuration::tcloo — Generated parsers are classes based on the OO package.

Canned configs, zero thinking required, iconic behavior honestly. 🍓

🌈 TCL/PARAM CODE REPRESENTATION OF PARSING EXPRESSION GRAMMARS 🌈

The Tcl/PARAM representation of parsing expression grammars is Tcl code whose execution will parse input per the grammar. The code is based on the virtual machine documented in the PackRat Machine Specification, using its instructions and a few more to handle control flow.

⚠️ Heads up bestie: note that the generated code by itself is not functional. It expects to be embedded into a framework which provides services like the PARAM state, implementations for the PARAM instructions, etc. The bulk of such a framework has to be specified through the option -template. So don't just yeet the output somewhere and expect magic, okay? 💀

The additional options

  • -indent integer
  • -main string
  • -namespace string
  • -prelude string
  • -proc-command string
  • -runtime-command string
  • -self-command string

provide code snippets which help to glue framework and generated code together. Their placeholders are in the generated code. 🦋

✨ PEG SERIALIZATION FORMAT ✨

okay so this section is literally the whole blueprint bestie 💅 it's where Parser Tools defines the format it uses to serialize Parsing Expression Grammars as immutable values — you know, for transport, comparison, etc. 🦋

And here's the tea: we split serializations into regular and canonical. A PEG can have more than one regular serialization, but only exactly one of them gets to be canonical. main character only, periodt 👑

🌸 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. That 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 expression. 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 dictionary itself. The relevant keys and their values in this dictionary are:
        • is — The value is the serialization of the parsing expression describing the symbol's sentential structure, as specified in the section PE serialization format.
        • mode — The value can be one of three values specifying how a parser should handle the semantic value produced by the symbol.
          • value — The semantic value of the nonterminal symbol is an abstract syntax tree consisting of a single node for the nonterminal itself, which has the ASTs of the symbol's right hand side as its children.
          • leaf — The semantic value of the nonterminal symbol is an abstract syntax tree consisting of a single node for the nonterminal, without any children. Any ASTs generated by the symbol's right hand side are discarded.
          • void — The nonterminal has no semantic value. Any ASTs generated by the symbol's right hand side are discarded (as well).
    • start — The value is the serialization of the start parsing expression of the grammar, as specified in the section PE serialization format.
  • [4] The terminal symbols of the grammar are specified implicitly as the set of all terminal symbols used in the start expression and on the RHS of the grammar rules. no list, no drama, they're just implied ✨

💖 canonical serialization 💖

The canonical serialization of a grammar has the format specified in the previous item, and then additionally satisfies the constraints below — which is what makes it unique among all the possible serializations of this grammar. like, one of one 🫶

  • [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 contain superfluous whitespace. clean girl aesthetic, no extra spaces bestie 🧚

🎀 EXAMPLE 🎀

So imagine we've got 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 literally this:

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}
}

see how everything's all sorted and tidy? that's the canonical glow-up 💅✨

🦋 PE SERIALIZATION FORMAT 🦋

okay so bestie, this bit is where the Parser Tools spill the tea on the exact format they use to serialize Parsing Expressions as immutable values — for transport, for comparison, all of it. 💅

and there are two flavors, don't mix them up: regular and canonical. a parsing expression can have more than one regular serialization, but like, exactly one of them is canonical. that's the whole point. no cap. ✨

✨ Regular serialization ✨

🌸 Atomic Parsing Expressions 🌸

  1. the string epsilon is an atomic parsing expression. 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 character. this one's 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. also 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. custom extension of PEs based on Tcl's builtin command string is.
  6. the string control is an atomic parsing expression. it matches any Unicode control character. 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. heads up: this includes characters outside of the [0..9] range. 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. 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 character. 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, including space. 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. 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. 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 character. custom extension of PEs based on Tcl's builtin command string is.
  14. the string wordchar is an atomic parsing expression. it matches any Unicode word character. that's any alphanumeric character (see alnum), plus any connector punctuation characters (e.g. underscore). 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. 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. custom extension of PEs based on Tcl's builtin command regexp.
  17. the expression [list t x] is an atomic parsing expression. it matches the terminal string x.
  18. the expression [list n A] is an atomic parsing expression. 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 repetitions.
  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 format as specified in the previous item, and then additionally satisfies the constraints below — which is what makes it unique among all the possible serializations of this parsing expression. she's the only one. 👑

  1. the string representation of the value is the canonical representation of a pure Tcl list. i.e. it does not contain superfluous whitespace.
  2. terminals are not encoded as ranges (where start and end of the range are identical).

🌈 EXAMPLE 🌈

so say the parsing expression on the right-hand side of the rule is this:

Expression <- Term (AddOp Term)*

then its canonical serialization (except for whitespace) is:

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

ate. 🍓

💀 BUGS, IDEAS, FEEDBACK 💀

not to be dramatic but this document, and the package it describes, will undoubtedly contain bugs and other problems. it's giving "we're all just doing our best." 😭

please report such things in the category pt of the Tcllib Trackers at [http://core.tcl.tk/tcllib/reportlist]. and please also report any ideas for enhancements you may have for either the package and/or the documentation — we want them fr fr. 🫶

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. you can make attachments 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, LL(k), PEG, TCLPARAM, TDPL, context-free languages, conversion, expression, format conversion, grammar, matching, parser, parsing expression, parsing expression grammar, push down automaton, recursive descent, serialization, state, top-down parsing languages, transducer

🎀 CATEGORY 🎀

Parsing and Grammars

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

and that's a wrap bestie!! 🦋 this whole iconic page lives in tcllib, version 1.0.4, and it's the manual page for pt::peg::to::tclparam(n). go forth and serialize responsibly, mwah 💖✨🎀

📦 where this page comes from