;;; Alef Lazily Evaluates Functions
;;; (C) 2008-2009 Dr. Gergo ERDI <http://gergo.erdi.hu/>

(in-package :alef)

(deftype typedesc () 'tree)
(deftype requirement () 'list)

(defun type-fun-p (type)
  (declare (typedesc type))
  (and (consp type) (eq (car type) 'fun)))

(defun type-supertype (type)
  (declare (typedesc type))
  (typecase type
    (cons (car type))
    (atom type)))

(defun make-typevar ()
  (gensym "T"))

(defclass signature ()
  ((type :type typedesc :initarg :type :reader signature-type)
   (requirements :type list :initarg :reqs :reader signature-reqs)))

(defun make-signature (type &optional reqs)
  (make-instance 'signature :type type :reqs reqs))

(defclass typing ()
  ((signature :initarg :signature :type signature :reader typing-signature)
   (equations :initarg :equations :type list :reader typing-equations)))

(defun make-typing (signature &optional equations)
  (declare (signature signature))
  (make-instance 'typing :signature signature :equations equations))

(defclass typeinfo ()
  ((symbol :initarg :symbol :reader typeinfo-symbol :type symbol)
   (params :initarg :params :reader typeinfo-params :type list)
   (constructors :initform (list) :accessor typeinfo-constructors :type list)))

(defun make-typeinfo (symbol params)
  (make-instance 'typeinfo :symbol symbol :params params))

(defclass constructor-info ()
  ((symbol :initarg :symbol :reader constructor-symbol :type symbol)
   (supertype :initarg :supertype :reader constructor-type :type symbol)
   (signature :initarg :signature :reader constructor-signature :type signature)))

(defun make-constructor (symbol supertype signature)
  (make-instance 'constructor-info :symbol symbol :supertype supertype :signature signature))