;; lang2.ss
;; Doug Blank

(load "petite-init.ss")
(load "sllgen.ss")

(define scanner
  '((whitespace (whitespace) skip)
    (comment ("%" (arbno (not #\newline))) skip)
    (identifier (letter (arbno (or letter digit))) make-symbol)
    (number (digit (arbno digit)) make-number)))

(define grammar
  '((statement
      ("{" statement ";" statement "}")
      compound-statement)
    (statement
      ("while" expression "do" statement)
      while-statement)
    (statement
      (identifier ":=" expression)
      assign-statement)
    (expression
      (number)
      lit-exp)
    (expression
      (identifier)
      var-exp)
    (expression
      ("let" (separated-list declaration ";") "in" expression)
      let-exp)
    (expression
      ("(" expression (arbno expression) ")")
      app-exp)
    (declaration
      (identifier "=" expression)
      decl)))

(define parse
  (sllgen:make-string-parser scanner grammar))

;; (parse "{x := foo; y := bar}")

(define repl
  (sllgen:make-rep-loop "--> " (lambda (x) x)
    (sllgen:make-stream-parser scanner grammar)))

(repl)