divisors returns empty list for 0

This is mainly for consistency with other words
(factors, group-factors, unique-factors)

diff --git a/basis/math/primes/factors/factors.factor b/basis/math/primes/factors/factors.factor
index dd73b0a073e1257b108e37fb14a59e7c639b8133..105bd5b976679c9bcdf238357793daaeb090c6e4 100644 (file)
--- a/basis/math/primes/factors/factors.factor
+++ b/basis/math/primes/factors/factors.factor
@@ -47,8 +47,10 @@ PRIVATE>
     dup 1 = [
         1array
     ] [
-        group-factors [ first2 [0,b] [ ^ ] with map ] map
-        [ product ] product-map natural-sort
+        group-factors dup empty? [
+            [ first2 [0,b] [ ^ ] with map ] map
+            [ product ] product-map natural-sort
+        ] unless
     ] if ;
 
 : unix-factor ( string -- )