You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
97 lines
2.5 KiB
Racket
97 lines
2.5 KiB
Racket
#lang racket/base
|
|
|
|
;; A language level for automatically generating parsers out of BNF grammars.
|
|
;;
|
|
;; Danny Yoo (dyoo@hashcollision.org)
|
|
;;
|
|
;; Intent: make it trivial to generate languages for Racket. At the
|
|
;; moment, I find it painful to use parser-tools. This library is
|
|
;; meant to make it less agonizing.
|
|
;;
|
|
;; The intended use of this language is as follows:
|
|
;;
|
|
;;;;; s-exp-grammar.rkt ;;;;;;;;;
|
|
;; #lang brag
|
|
;; s-exp : "(" s-exp* ")" | ATOM
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
|
|
|
|
;; What this generates is:
|
|
;;
|
|
;; * parse: a function that consumes a source and a
|
|
;; position-aware lexer, and produces a syntax object.
|
|
;;
|
|
;; * make-rule-parser: a custom parser given a provided start rule.
|
|
;;
|
|
;; You'll still need to do a little work, by providing a lexer that
|
|
;; defines what the uppercased tokens mean. For example, you can
|
|
;; use the parser-tools/lex lexer tools:
|
|
;;
|
|
;; (require brag/support
|
|
;; parser-tools/lex
|
|
;; parser-tools/lex-sre)
|
|
;;
|
|
;; (define tokenize
|
|
;; (lexer-src-pos
|
|
;; [(:+ alphabetic)
|
|
;; (token 'ATOM lexeme)]
|
|
;; [whitespace
|
|
;; (return-without-pos (tokenize/1 input-port))]
|
|
;; [(:or "(" ")")
|
|
;; (token lexeme lexeme)]))
|
|
;;
|
|
|
|
;; However, that should be all you need. The output of an
|
|
;; generated grammar is an honest-to-goodness syntax
|
|
;; object with source locations, fully-labeled by the rules.
|
|
;;
|
|
;; (parse (tokenize an-input-port))
|
|
;;
|
|
;;
|
|
|
|
;; The first rule is treated as the start rule; any successful parse
|
|
;; must finish with end-of-file.
|
|
|
|
|
|
;; Terminology:
|
|
;;
|
|
|
|
|
|
;; A rule is a rule identifier, followed by a colon ":", followed by a
|
|
;; pattern.
|
|
|
|
;; A rule identifier is an identifier that is not in upper case.
|
|
;; A rule identifier should follow the Racket rules for identifiers,
|
|
;; except that it can't contain * or +.
|
|
;;
|
|
;; A token is a rule identifier that is all in upper case.
|
|
|
|
|
|
|
|
;; A pattern may either be
|
|
;;
|
|
;; * an implicit sequence of patterns,
|
|
;;
|
|
;; * a literal string,
|
|
;;
|
|
;; * a rule identifier,
|
|
;;
|
|
;; * a quanitifed pattern, either with "*" or "+",
|
|
;;
|
|
;; * an optional pattern: a pattern surrounded by "[" and "]", or
|
|
;;
|
|
;; * a grouped sequence: a pattern surrounded by "(" and ")".
|
|
|
|
|
|
(require (for-syntax racket/base
|
|
"codegen.rkt"))
|
|
|
|
(provide rules
|
|
(rename-out [#%plain-module-begin #%module-begin])
|
|
#%top-interaction)
|
|
|
|
(define-syntax (rules stx)
|
|
(rules-codegen #:parser-provider-module 'brag/cfg-parser/cfg-parser ;; 'parser-tools/yacc
|
|
#:parser-provider-form 'cfg-parser ;; 'parser
|
|
stx))
|