I'm just learning how to use cl-unification. I have written some code that doesn't work the way I expect, but of course this probably means that my expectations are wrong.

Can one of the cl-unification gurus take a look, and let me know what I'm doing wrong?

Thanks,

-russ

(defpackage :unification-demo (:use :cl :CL.EXT.DACF.UNIFICATION))

(in-package :unification-demo)

(declaim (optimize (debug 3) (speed 0)))

(defclass call-expr () ((rator :reader rator) (rands :reader rands)))

(defmethod initialize-instance :after ((call-expr call-expr) &key form) (with-slots (rator rands) call-expr (destructuring-bind (rator-form &rest rand-forms) form (setf rator rator-form rands (mapcar (lambda (rand-form) (parse-expr rand-form)) rand-forms)))))

(defclass var-ref () ((var :initarg :var :reader var)))

(defclass let-binding () ((var :reader let-binding-var :initarg :var) (expr :reader let-binding-expr :initarg :expr)))

(defmethod initialize-instance :after ((let-binding let-binding) &key form) (with-slots (var expr) let-binding (destructuring-bind (var-form expr-form) form (setf var var-form expr (parse-expr expr-form)))))

(defclass let-expr () ((bindings :reader bindings) (body :reader body)))

(defmethod initialize-instance :after ((let-expr let-expr) &key form) (with-slots (bindings body) let-expr (destructuring-bind (binding-forms body-form) (cdr form) (setf bindings (mapcar (lambda (form) (make-instance 'let-binding :form form)) binding-forms) body (parse-expr body-form)))))

(defun parse-expr (form) (flet ((car-match (indicator) (and (consp form) (eql (car form) indicator))) (constant-match () (or (stringp form) (numberp form)))) (cond ((constant-match) form) ((car-match 'let) (make-instance 'let-expr :form form)) ((car-match 'lambda) (make-instance 'lambda-expr :form form)) ((consp form) (make-instance 'call-expr :form form)) ((symbolp form) (make-instance 'var-ref :var form)) (t (error "unhandled form ~A" form)))))

;; this works (find-variable-value '?bs (unify #T(let-expr bindings ?bs) (parse-expr '(let ((x 1) (y 2)) (+ x y)))))

;; this fails, why? (find-variable-value '?b (unify #T(let-expr bindings (list ?b &rest ?bs)) (parse-expr '(let ((x 1) (y 2)) (+ x y)))))