object: change to a stateful table

1 files changed, 36 insertions, 0 deletions

diff --git a/set.scm b/set.scm
index 52d10b6..6aa661d 100644
--- a/set.scm
+++ b/set.scm
@@ -467,6 +467,42 @@
           smap
           pairs)))
 
+;;; SYMBOL-TABLE:
+;;; 
+;;; A stateful map from symbols to values.
+;;; 
+;;; (SET! KEY VAL)
+;;; (DELETE! KEY)
+;;; (GET KEY)
+;;; (TYPE)
+(define symbol-table
+  (lambda ()
+    (let ((table '()))
+      (letrec ((insert!
+                (lambda (key val)
+                  (let ((ret (smap:insert table
+                                          (symbol->string key)
+                                          val)))
+                    (set! table (car ret))
+                    (cdr ret))))
+               (delete! (lambda (key) (smap:delete table (symbol->string
+                                                          key))))
+               (search
+                (lambda (key . default)
+                  (let ((ret (smap:search table (symbol->string key))))
+                    (if (null? ret)
+                        (if (null? default)
+                            #f
+                            (car default))
+                        (map:val ret))))))
+        (lambda (op . args)
+          (cond
+            ((eq? op 'set!) (apply insert! args))
+            ((eq? op 'delete!) (apply delete! args))
+            ((eq? op 'get) (apply search args))
+            ((eq? op 'type) 'symbol-table)
+            (else (error 'symbol-table 'unknown op args))))))))
+
 ;;; ;;;;;
 ;;; Tests
 ;;; ;;;;;