(defpackage #:abs-syn
  (:use #:openlisp)
  (:export
   #:<exp-int>
   #:<exp-var>
   #:<exp-str>
   #:<exp-unr>
   #:<exp-bin>
   #:<cmd-rem>
   #:<cmd-goto>
   #:<cmd-print>
   #:<cmd-input>
   #:<cmd-if>
   #:<cmd-let>
   #:<phrase-line>
   #:<phrase-list>
   #:<phrase-run>
   #:<phrase-p-end>
   #:priority-uop
   #:priority-binop))
(in-package #:abs-syn)

;; If these were only C enums, without any payload, I'd just use symbols and (error) in the t case.
;; But classes seem better for the associated data, in discriminated unions.

(defclass <expression> () () (:abstractp t))
(defclass <exp-int> (<expression>) ((int :accessor int)))
(defclass <exp-var> (<expression>) ((var :accessor var)))
(defclass <exp-str> (<expression>) ((str :accessor str)))
(defclass <exp-unr> (<expression>) ((op :accessor op) (exp :accessor exp)))
(defclass <exp-bin> (<expression>) ((exp1 :accessor exp1) (op :accessor op) (exp2 :accessor exp2)))

(defclass <command> () () (:abstractp t))
(defclass <cmd-rem> (<command>) ((rem :accessor rem)))
(defclass <cmd-goto> (<command>) ((goto :accessor goto)))
(defclass <cmd-print> (<command>) ((expr :accessor expr)))
(defclass <cmd-input> (<command>) ((var :accessor var)))
(defclass <cmd-if> (<command>) ((expr :accessor expr) (num :accessor num)))
(defclass <cmd-let> (<command>) ((var :accessor var) (expr :accessor expr)))

(defclass <line> () ((num :accessor num) (cmd :accessor cmd)))

(defclass <phrase> () () (:abstractp t))
(defclass <phrase-line> (<phrase>) ((line :accessor line)))
(defclass <phrase-list> (<phrase>) ())
(defclass <phrase-run> (<phrase>) ())
(defclass <phrase-p-end> (<phrase>) ())

(defun priority-uop (unr-op)
  (case unr-op
    ((not) 1)
    ((uminus) 7)))

(defun priority-binop (bin-op)
  (cond ((member bin-op '(mult div)) 6)
    ((member bin-op '(plus minus)) 5)
    ((eql bin-op 'mod) 4)
    ((member bin-op '(equal less lesseq great greateq diff)) 3)
    ((member bin-op '(and or)) 2)))
(provide "abs-syn")