Accept standard EBNF

[apalala]

There are many grammars and tools out there using the same variation of EBNF, and TatSu should be able to parse it.

Examples:

• https://www.bottlecaps.de/rr/ui
• https://github.com/python/cpython/blob/master/Grammar/Grammar

Changes required:

• Accepting :=, :=, and : for introducing the right hand side of rules
• Accept ()* and ()+ for closures
• Not require a ; to end a rule (indented expressions belong to the rule)
• Accept /* ... */ comments

[mgrazebrook]

I'd like this! Every time I come back to Tatsu, I find myself instinctively using : instead of = for rules.

[apalala]

The ISO standard, which I don't think is the one people are used to:

https://en.wikipedia.org/wiki/Extended_Backus–Naur_form#Syntax_diagram

Minimalistic (classic?) version:

grammar  : ( rule | NEWLINE )*
rule     : NAME ':' rhs NEWLINE
rhs      : alt ( '|' alt )*
alt      : item+
item     : '[' rhs ']' | atom [ '*' | '+' ]
atom     : '(' rhs ')' | NAME | STRING

Comparison of Symbols

Resource                Assignment    Repetition    Optional
Tomassetti              :                       * / +               ?
EasyExtend             :                       * / +               [ ]
Wirth (Classic)       =                       { }                 [ ]
ISO (Wikipedia)      =                       { }                 [ ]

[apalala]

Authoritative Standards & Definitions

International Standard EBNF Syntax Notation (ISO/IEC 14977) International Standard EBNF Syntax Notation (ISO/IEC 14977)

EBNF - Wikipedia (Self-Describing Grammar Section) EBNF - Wikipedia (Self-Describing Grammar Section)

Minimalist & Tool-Oriented Grammars

Federico Tomassetti - EBNF Grammars Collection Federico Tomassetti - EBNF Grammars Collection

EasyExtend EBNF Grammars EasyExtend EBNF Grammars

GitHub Gist: EBNF for C and JavaScript GitHub Gist: EBNF for C and JavaScript

Historical & Classic References

Wirth's Original EBNF (Pascal for Small Machines) Wirth's Original EBNF (Pascal for Small Machines)

EBNF: A Notation to Describe Syntax (PDF Guide) EBNF: A Notation to Describe Syntax (PDF Guide)