Trying to debug abstract classes, WIP

3 files changed, 27 insertions, 6 deletions

diff --git a/cabs-syn.lisp b/cabs-syn.lisp
index 12b9fd4..2b6d30a 100644
--- a/cabs-syn.lisp
+++ b/cabs-syn.lisp
@@ -24,7 +24,10 @@
 ;; But classes seem better for the associated data, in discriminated unions.
 
 (defclass <expression> () () (:metaclass <abstract-class>))
-(defclass <exp-int> (<expression>) ((int :accessor int)))
+
+(defclass <exp-int> (<expression>) ((my-int :accessor my-int)))
+;; TODO: need another closer-mop:validate-superclass call here
+
 (defclass <exp-var> (<expression>) ((var :accessor var)))
 (defclass <exp-str> (<expression>) ((str :accessor str)))
 (defclass <exp-unr> (<expression>) ((op :accessor op) (exp :accessor exp)))
diff --git a/cbasic.lisp b/cbasic.lisp
index 706c564..1085e16 100644
--- a/cbasic.lisp
+++ b/cbasic.lisp
@@ -1,11 +1,26 @@
 ;;; I'm trying to write an interpreter for a BBC BASIC subset
 ;;; initially following the design of
 ;;; https://caml.inria.fr/pub/docs/oreilly-book/html/book-ora058.html
-;;; and later I can Frankenstein it with
-;;; https://github.com/Henry/BuddKaminInterpreters
+;;; then later I can optimise following
+;;; https://github.com/Henry/BuddKaminInterpreters and
+;;; https://oleksandrmanzyuk.wordpress.com/2014/06/18/from-object-algebras-to-finally-tagless-interpreters-2/
+;;;
+;;; A BASIC interpreter already exists at
+;;; https://gitlab.com/com-informatimago/com-informatimago/-/tree/master/small-cl-pgms/basic
+;;; but it is idiomatic CL,
+;;; whereas I'm experimenting with a subset like ISLisp.
 
+;; Because this is the main package,
+;; 1) ql:quickload QuickLisp dependencies and
+;; 2) load local dependencies here.
 (load "cutil.lisp")
 (load "cparse.lisp")
+;; Use require & defpackage in each package from then on.
+;; NB: must have no circular dependencies, and topologically sort the loads.
+;;
+;; TODO: it's easier to just get started with ASDF
+;;       ( https://lisp-lang.org/learn/writing-libraries )
+
 (require "cparse")
 (require "")
 (defpackage #:cbasic
diff --git a/cutil.lisp b/cutil.lisp
index 0b569e2..2f10099 100644
--- a/cutil.lisp
+++ b/cutil.lisp
@@ -1,11 +1,14 @@
 (defpackage #:cutil
-  (:use #:common-lisp)
+  (:use #:common-lisp :closer-mop)
   (:export
    #:<abstract-class>))
 (in-package #:cutil)
 
-(defclass <abstract-class> () ())
+(defclass <abstract-class> (standard-class) ())
 (defmethod make-instance ((self <abstract-class>) &key)
-  (error "Cannot instantiate abstract class ~A" (class-name c)))
+  (error "Cannot instantiate abstract class ~A" (class-name self)))
+(defmethod closer-mop:validate-superclass ((class <abstract-class>)
+					   (superclass standard-class))
+  t)
 
 (provide "cutil")