I have to edit lots of grammar files in .bnf format. Is there a mode for this in Emacs?
I ve looked at CEDET s semantic package, and it seems that it USED to have a bnf-mode, but not any more. This snippet is googlable, but semantic-bnf-mode doesn t seem to exist:
(autoload semantic-bnf-mode "semantic-bnf" "Mode for Bovine Normal Form." t)
(add-to-list auto-mode-alist ("\.bnf$" . semantic-bnf-mode))
Thanks Don. I improved the code very slightly, here s a new version.
(define-generic-mode bnf-mode
() ;; comment char: inapplicable because # must be at start of line
nil ;; keywords
(
("^#.*" . font-lock-comment-face) ;; comments at start of line
("^<.*?>" . font-lock-function-name-face) ;; LHS nonterminals
("<.*?>" . font-lock-builtin-face) ;; other nonterminals
("::=" . font-lock-const-face) ;; "goes-to" symbol
("|" . font-lock-warning-face) ;; "OR" symbol
("{:\|:}" . font-lock-keyword-face) ;; special pybnf delimiters
)
("\.bnf\ " "\.pybnf\ ") ;; filename suffixes
nil ;; extra function hooks
"Major mode for BNF highlighting.")
The Semantic bnf mode was for its own internal parser format. The original bnf name was a pun that ended up confusing people.
The existing Semantic modes such as wisent-grammar-mode and bovine-grammar-mode are for the grammars used by CEDET, and the original bnf-mode was similar, and did not represent a real BNF style grammar.
You are probably more interested in ebnf2ps, which translates ebnf grammars (yacc, etc) into syntax charts, though I haven t used it myself.
To be more readable and findable as an answer, jmmcd answered his own question with the following. You can find more in the emacs Help > elisp > 23.2.6 Generic Modes.
"I put this in my .emacs and it seems to work."
(define-generic-mode bnf-mode
("#")
nil
(("^<.*?>" . font-lock-variable-name-face)
("<.*?>" . font-lock-keyword-face)
("::=" . font-lock-warning-face)
("|" . font-lock-warning-face))
("\.bnf\.pybnf\ ")
nil
"Major mode for BNF highlighting.")
I just created a GNU Emacs major mode for editing BNF grammars.
Currently provides basic syntax and font-locking for BNF files. EBNF and ABNF are in my plans for the near future.
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