; COSC 152
; Fall 2005
; Dennis Brylow
;
; Lecture 20 Demo
; Scanner specification and grammer for a parser.

(define scanner-spec-lec20
  '((white-sp (whitespace)        skip)
    (comment   (";" (arbno (not #\newline)))   skip)
    (identifier (letter (arbno (or letter digit "?" "*" "_")))  symbol)
    (number (digit (arbno digit)) number))
)  
  
  
(define grammar-lec20 
  '((expr (number) lit-expr)
    (expr (identifier) var-expr)
    (expr ("(" subexpr ")") sub-expr)
    (subexpr ("if" expr expr expr) if-expr)
    (subexpr ("lambda" "(" (arbno identifier) ")" expr) lambda-expr)
    (subexpr (expr (arbno expr)) app-expr)
     ))

(define scan&parse (sllgen:make-string-parser scanner-spec-lec20 grammar-lec20))
(sllgen:make-define-datatypes scanner-spec-lec20 grammar-lec20)