; -*- Hen -*-
;;;
;;;; Simple calculator in Scheme
;;;
;;
;; @created   "Tue Jan  6 12:47:23 2004"
;; @modified  "Mon Oct 25 11:07:24 2004"
;; @author    "Dominique Boucher"
;; @copyright "Dominique Boucher"
;;
;; Simple arithmetic calculator. 
;; 
;;   This program illustrates the use of the lalr-scm parser generator
;; for Scheme. It is NOT robust, since calling a function with 
;; the wrong number of arguments may generate an error that will
;; cause the calculator to crash.


;;;
;;;;   The LALR(1) parser
;;;

(require-extension lalr)

(define calc-parser
  (lalr-parser

   ;; --- Options 
   ;; output a parser, called calc-parser, in a separate file - calc.yy.scm, 
   (output:    calc-parser "calc.yy.scm")
   ;; output the LALR table to calc.out
   (out-table: "calc.grm.out")

   ;; --- token definitions
   (ID NUM NEWLINE  LPAREN RPAREN
       (nonassoc: =)
       (left: - +)
       (left: * /)
       (left: COMMA)
       (nonassoc: uminus))

   (lines    (lines line) : (display-result $2)
             (line)       : (display-result $1))


   ;; --- rules
   (line     (NEWLINE)               : (void)
	     (assign NEWLINE)        : $1
             (expr   NEWLINE)        : $1
             (error  NEWLINE)        : #f)

   (assign   (ID = expr)             : (add-binding $1 $3))

   (expr     (NUM)                   : $1
             (ID)                    : (get-binding $1)
	     (ID LPAREN RPAREN)      : (invoke-proc $1 (list))
	     (ID LPAREN args RPAREN) : (invoke-proc $1 $3)
	     (expr + expr)           : (+ $1 $3)
             (expr - expr)           : (- $1 $3)
             (expr * expr)           : (* $1 $3)
             (expr / expr)           : (/ $1 $3)
             (- expr (prec: uminus)) : (- $2)
	     (LPAREN expr RPAREN)    : $2)

   (args     (expr)                  : (list $1)
             (args COMMA expr)       : (cons $3 $1))))