pt::peg::to::container(3tcl)

📦

version 2.0 · 2 versions

2.0 · debian trixie, ubuntu questing, ubuntu resolute, ubuntu stonking (latest)
1.21 · debian bookworm, ubuntu jammy, ubuntu noble

, in debian trixie, ubuntu questing, ubuntu resolute, ubuntu stonking

👑 pt::peg::to::container 👑

okay bestie so this is a page from Parser Tools, and the manual name is pt::peg::to::container — yes it's a mouthful, yes it's iconic, we move.

✨ NAME ✨

pt::peg::to::container — PEG Conversion. Write CONTAINER format. that's it, that's the whole vibe 🎀

💖 SYNOPSIS 💖

package require Tcl 8.5 9

package require pt::peg::to::container ?1.1?

package require pt::peg

package require text::write

package require char

pt::peg::to::container reset

pt::peg::to::container configure

pt::peg::to::container configure option

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

pt::peg::to::container convert serial

🦋 DESCRIPTION 🦋

Are you lost ? Do you have trouble understanding this document ? 🥺 bestie if that's you, no worries at all — go read the overview in the Introduction to Parser Tools. That doc is literally the entrypoint to the whole system this package is part of. iykyk.

This package implements the converter from parsing expression grammars to CONTAINER markup. 💅

It resides in the Export section of the Core Layer of Parser Tools, and can be used either directly with the other packages of this layer, or indirectly through the export manager provided by pt::peg::export. The latter is intented for use in untrusted environments and done through the corresponding export plugin pt::peg::export::container sitting between converter and export manager. she's a middleman, she's a connector, she's doing her job 💖

IMAGE: arch_core_eplugins

🌈 API 🌈

The API provided by this package satisfies the specification of the Converter API found in the Parser Tools Export API specification. no cap, she follows the rules 👑

pt::peg::to::container reset — This command resets the configuration of the package to its default settings. factory reset era 🧚
pt::peg::to::container configure — This command returns a dictionary containing the current configuration of the package. it's giving "tell me everything" 🍓
pt::peg::to::container 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::container 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. glow-up time ✨
pt::peg::to::container 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 CONTAINER markup encoding the grammar, per the current package configuration. The created string is then returned as the result of the command. main character energy fr fr 💅

🎀 OPTIONS 🎀

The converter to the CONTAINER format recognizes the following options and changes its behaviour as they specify. yes, she's flexible, she's adaptable, we love that for her 💜

-file string — The value of this option is the name of the file or other entity from which the grammar came, for which the command is run. The default value is unknown. 🫶
-name string — The value of this option is the name of the grammar we are processing. The default value is a_pe_grammar. iconic default, honestly 💖
-user string — The value of this option is the name of the user for which the command is run. The default value is unknown. 🦋
-mode bulk|incremental — The value of this option controls which methods of pt::peg::container instances are used to specify the grammar, i.e. preload it into the container. There are two legal values, as listed below. The default is bulk. pick your fighter ⚔️
- 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 expressions.

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 nonterminal having its own block of defining commands. one at a time, baby steps, we love a slow reveal 🌸

-template string — The value of this option is a string into which to put the generated code 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@". it's a fill-in-the-blanks situation bestie 🎀
- @user@ — To be replaced with the value of the option -user.
- @format@ — To be replaced with the the constant CONTAINER. (yes, the original says "the the", we don't edit the sacred texts 💀)
- @file@ — To be replaced with the value of the option -file.
- @name@ — To be replaced with the value of the option -name.
- @mode@ — To be replaced with the value of the option -mode.
- @code@ — To be replaced with the generated code.

🌟 GRAMMAR CONTAINER 🌟

The container format is another form of describing parsing expression grammars. While data in this format is executable it does not constitute a parser for the grammar. It always has to be used in conjunction with the package pt::peg::interp, a grammar interpreter. so like… she's the blueprint, not the building 🏗️

The format represents grammars by a snit::type, i.e. class, whose instances 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. that's it, that's the tea ☕

🌸 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 ✨

okay bestie, this is the part where we talk about how Parser Tools turns a Parsing Expression Grammar into an immutable value so you can yeet it around for transport, comparison, whatever. 💅

so there's two flavors of serialization, and you need to know the difference:

regular serialization — a PEG can have more than one of these, no big deal
canonical serialization — exactly one of these exists, it's the main character 👑

💖 regular serialization 💖

The serialization of any PEG is a nested Tcl dictionary. fr fr, that's the whole vibe.
This dictionary holds a single key, pt::grammar::peg, and its value. That value holds the contents of the grammar.
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. no duplicates allowed bestie.
  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 symbols sentennial 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 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 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.
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.

🦋 canonical serialization 🦋

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

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.
The string representation of the value is the canonical representation of a Tcl dictionary. I.e. it does not contain superfluous whitespace. clean. tidy. immaculate. ✨

🌸 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}
}

like, look at that dictionary. sorted, tidy, no cap. the lsort -increasing -dict energy is immaculate 🫶

Okay bestie, let's get into the serialization format that Parser Tools uses to turn Parsing Expressions into immutable values — you know, for transport, comparison, and all that. ✨

So there are two kinds: regular and canonical serializations. A parsing expression can have more than one regular serialization, but only exactly one of them is canonical. Periodt. 💅

✨ Regular serialization ✨

🔤 Atomic Parsing Expressions 🔤

epsilon is an atomic parsing expression — it matches the empty string. 🫧
dot is an atomic parsing expression — it matches any character. 💫
alnum is an atomic parsing expression — it matches any Unicode alphabet or digit character. This is a custom extension of PEs based on Tcl's builtin command string is. 👑
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. 🦋
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. 🌈
control is an atomic parsing expression — it matches any Unicode control character. This is a custom extension of PEs based on Tcl's builtin command string is. 🎀
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. 🔥
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. 🌸
lower is an atomic parsing expression — it matches any Unicode lower-case alphabet character. This is a custom extension of PEs based on Tcl's builtin command string is. 💜
print is an atomic parsing expression — it matches any Unicode printing character, including space. This is a custom extension of PEs based on Tcl's builtin command string is. 🖨️
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. ❗
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. 🫧
upper is an atomic parsing expression — it matches any Unicode upper-case alphabet character. This is a custom extension of PEs based on Tcl's builtin command string is. 👑
wordchar is an atomic parsing expression — it matches any Unicode word character. This is any alphanumeric character (see alnum), and any connector punctuation characters (e.g. underscore). This is a custom extension of PEs based on Tcl's builtin command string is. 🔤
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. 🔢
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. 💯
The expression [list t x] is an atomic parsing expression — it matches the terminal string x. 🎯
The expression [list n A] is an atomic parsing expression — it matches the nonterminal A. 🎯

🌟 Combined Parsing Expressions 🌟

For parsing expressions e1, e2, ... the result of [list / e1 e2 ... ] is a parsing expression too. This is the ordered choice, aka prioritized choice. 💅
For parsing expressions e1, e2, ... the result of [list x e1 e2 ... ] is a parsing expression too. This is the sequence. 🔗
For a parsing expression e the result of [list * e] is a parsing expression too. This is the kleene closure, describing zero or more repetitions. 🔁
For a parsing expression e the result of [list + e] is a parsing expression too. This is the positive kleene closure, describing one or more repetitions. 🔂
For a parsing expression e the result of [list & e] is a parsing expression too. This is the and lookahead predicate. 👀
For a parsing expression e the result of [list ! e] is a parsing expression too. This is the not lookahead predicate. 🙅
For a parsing expression e the result of [list ? e] is a parsing expression too. This is the optional input. ❓

💎 Canonical serialization 💎

The canonical serialization of a parsing expression follows the format we just described, but then it also satisfies these extra constraints — which make it unique among all possible serializations of that parsing expression. 💎

The string representation of the value is the canonical representation of a pure Tcl list. I.e. it does not contain superfluous whitespace. 🧼
Terminals are not encoded as ranges (where start and end of the range are identical). 🚫

📝 EXAMPLE 📝

So like, if you have this parsing expression on the right-hand side of the rule:

Expression <- Term (AddOp Term)*

then its canonical serialization (ignoring whitespace) is:

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

Slay. 💅

🐞 BUGS, IDEAS, FEEDBACK 🐞

Okay so real talk: this doc and the package it describes will have bugs and other problems. 🙈 Please report them in the category pt of the Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Also, if you have ideas for enhancements for either the package and/or the documentation, send those too! 💡

When you propose code changes, please provide unified diffs, i.e. the output of diff -u. 📝

Also note: attachments are strongly preferred over inlined patches. You can attach files by going to the Edit form of the ticket right after creating it, and then using the left-most button in the secondary navigation bar. 📎

🔑 KEYWORDS 🔑

CONTAINER
EBNF
LL(k)
PEG
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 — that's the category, bestie. 📂

That's a wrap! This page is from tcllib version 1.1, for pt::peg::to::container(3tcl). Stay iconic, bestie! 💅✨

📦 where this page comes from

debian trixie: tcllib 2.0+dfsg-4 · Tcl
ubuntu questing: tcllib 2.0+dfsg-4
ubuntu resolute: tcllib 2.0+dfsg-5 · Tcl
ubuntu stonking: tcllib 2.0+dfsg-6 · Tcl
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-14: a language model's rewrite of the original, under its terms

pt::peg::to::container(3tcl)

👑 pt::peg::to::container 👑

✨ NAME ✨

💖 SYNOPSIS 💖

🦋 DESCRIPTION 🦋

🌈 API 🌈

🎀 OPTIONS 🎀

🌟 GRAMMAR CONTAINER 🌟

🌸 EXAMPLE 🌸

✨ PEG SERIALIZATION FORMAT ✨

💖 regular serialization 💖

🦋 canonical serialization 🦋

🌸 EXAMPLE 🌸

✨ Regular serialization ✨

🔤 Atomic Parsing Expressions 🔤

🌟 Combined Parsing Expressions 🌟

💎 Canonical serialization 💎

📝 EXAMPLE 📝

🐞 BUGS, IDEAS, FEEDBACK 🐞

🔑 KEYWORDS 🔑

📂 CATEGORY 📂

©️ COPYRIGHT ©️