tisp

commit 8eec941624c1c1b8cc600b0885760beb97047f7a
parent f5f83015e4af8f3def601e7f077b94cea3d77364
Author: Ed van Bruggen <edvb@uw.edu>
Date:   Fri, 20 Mar 2020 01:47:33 -0700

Add default function to return a val if given nil

Diffstat:
tibs/lib.tsp
 | 
8
++++++++

1 file changed, 8 insertions(+), 0 deletions(-)
diff --git a/tibs/lib.tsp b/tibs/lib.tsp
@@ -87,6 +87,14 @@
   `(unless ,expr
         (error 'assert "assertion " ',expr " failed")))
 
+; TODO support any sized list n depending on size of optional val
+(define (default n val)
+  (cond
+    ((nil? n) val)
+    ((and (pair? n) (nil? (cdr n)))
+     (car n))
+    (else (error 'default "expected only 1 optional argument"))))
+
 ;;; Control Flow
 ; TODO if b = pair and car b = else use cdr b
 (defmacro (if con a b)