1 files changed, 30 insertions, 0 deletions
diff --git a/runtime/printrec.lsp b/runtime/printrec.lsp
new file mode 100644
index 0000000..4ca17bb
--- /dev/null
+++ b/runtime/printrec.lsp
@@ -0,0 +1,30 @@
+; prints recursive list structure
+
+;(let (seen-list)
+(setf seenlist nil)
+  (defun seenp (l) (member l seenlist :test 'eq))
+  (defun make-seen (l) (setf seenlist (cons l seenlist)))
+  (defun printrec (l) (printrec-any l) (setf seenlist nil))
+  (defun printrec-any (l)
+    (cond ((atom l) (prin1 l) (princ " "))
+          ((seenp l) (princ "<...> "))
+          (t
+           (make-seen l)
+           (princ "(")
+           (printrec-list l)
+           (princ ") ")))
+     nil)
+  (defun printrec-list (l)
+    (printrec-any (car l))
+    (cond ((cdr l)
+           (cond ((seenp (cdr l))
+                  (princ "<...> "))
+                 ((atom (cdr l))
+                  (princ ". ")
+                  (prin1 (cdr l))
+                  (princ " "))
+                 (t
+                  (make-seen (cdr l))
+                  (printrec-list (cdr l))))))
+    nil)
+; )