; -*- Hen -*-

(require-extension lalr)

(define expr-parser
  (lalr-parser

   (output:    expr-parser "expr.grm.scm")

   ;; --- token definitions
   ( ID NUM IF THEN ELSE RPAREN  ;;LET
       (right: QUESTION COLON)
       (left: < > = >= <=)
       (left: + -)
       (left: * /)
       (left: uminus)
       (right: ^ ) 
       (left: LPAREN)
       )
   
   (expr     (NUM)                    : (exact->inexact (token-value $1))
             (ID)                     : (token-value $1)
	     (ID LPAREN RPAREN)       : `(,(token-value $1))
	     (ID LPAREN args RPAREN)  : `(,(token-value $1) . ,(reverse $3))
	     (expr + expr)            : `(+ ,$1 ,$3)
             (expr - expr)            : `(- ,$1 ,$3)
             (expr * expr)            : `(* ,$1 ,$3)
             (expr / expr)            : `(/ ,$1 ,$3)
             (- expr (prec: uminus))  : `(- ,$2)
             (expr ^ expr)            : `(pow ,$1 ,$3)
	     (expr < = expr)          : `(<= ,$1 ,$4)
	     (expr > = expr)          : `(>= ,$1 ,$4)
	     (expr <= expr)           : `(<= ,$1 ,$3)
	     (expr >= expr)           : `(>= ,$1 ,$3)
	     (expr > expr)            : `(> ,$1 ,$3)
	     (expr < expr)            : `(< ,$1 ,$3)
	     (expr QUESTION expr COLON expr) :  `(if ,$1 ,$3 ,$5) 
	     (IF  expr THEN expr ELSE expr)  :  `(if ,$2 ,$4 ,$6) 
	     (LPAREN expr RPAREN)     : $2 
	     )

   (args     (expr)                   : (list $1)
             (args expr)              : (cons $2 $1))

  ))