move rewriters to implementation file, make rewriter cycle-detecting

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/cuprate/implementation/alist-eq-map.scm b/lib/cuprate/implementation/alist-eq-map.scm
new file mode 100644
index 0000000..f9841e7
--- /dev/null
+++ b/lib/cuprate/implementation/alist-eq-map.scm
@@ -0,0 +1,21 @@
+(define (make-eq-map)
+  (define alist '())
+  (define interned-alist '())
+  (define counter 0)
+  (lambda (msg obj)
+    (case msg
+      ((contains?) (assq obj alist))
+      ((cycle-counter)
+       (set! interned-alist (cons obj interned-alist))
+       (let ((num (cdr (assq obj alist))))
+         (string->symbol (string-append
+                          "#"
+                          (number->string num)
+                          "#"))))
+      ((cycle-used?) (memq obj interned-alist))
+      ((intern!)
+       (set! alist (cons (cons obj counter) alist))
+       (set! counter (+ counter 1)))
+      (else (error 'make-eq-map
+                   "invalid message"
+                   msg)))))
\ No newline at end of file