(defpackage :toy-lang
  (:use :cl :clex2 :parse2))

(in-package :toy-lang)

(defun parse-foo (input)
  (parse (input)
    (:precedence (:right ":=")
                 (:left "+" "-")
                 (:left "*" "/"))
    (:precedence (:right ":=")
                 (:nonassoc "=" "/=" "<" ">" "<=" ">=")
                 (:left "+" "-")
                 (:left "*" "/"))
    (expr
     -> "defun" :identifier "(" (** "," :identifier) ")" expr => `(defun ,$2 ,$4 ,$6)
     -> "cond" clauses "end" => `(cond ,@$2)
     -> "begin" (** ";" expr) (? ";") "end" => `(progn ,@$2)
     -> expr ":=" expr => `(setq ,$1 ,$3)
     -> expr "=" expr => `(= ,$1 ,$3)
     -> expr "/=" expr => `(/= ,$1 ,$3)
     -> expr "<" expr => `(< ,$1 ,$3)
     -> expr ">" expr => `(> ,$1 ,$3)
     -> expr "<=" expr => `(<= ,$1 ,$3)
     -> expr ">=" expr => `(>= ,$1 ,$3)
     -> expr "+" expr => `(+ ,$1 ,$3)
     -> expr "-" expr => `(- ,$1 ,$3)
     -> expr "*" expr => `(* ,$1 ,$3)
     -> expr "/" expr => `(/ ,$1 ,$3)
     -> postfix)
    (postfix
          -> postfix "(" (** "," expr) ")" => `(,$1 ,@$3)
          -> postfix "[" (** "," expr) "]" => `(AREF ,$1 ,@$3)
          -> primary)
    (primary
          -> :identifier
          -> :number)

    ;;
    (clauses -> (** ";" clause) (? ";") => $1)
    (clause -> expr "->" expr => `(,$1 ,$3))

    (:number -> "[0-9]+" => (parse-integer $$))
    (:identifier -> "[a-zA-Z0-9]+" => (intern (string-upcase $$)))
    (-> "\\s+")))

;; (parse-foo "1+3+4") => (+ (+ 1 3) 4)
;; 
;; (parse-foo "defun fib(n) 
;;   cond 
;;     n < 2 -> n; 
;;     t -> fib(n-2) + fib(n-1)
;;   end")
;; => (DEFUN FIB (N) (COND ((< N 2) N) (T (+ (FIB (- N 2)) (FIB (- N 1))))))