Ensure that random-prime result has the right size

As noted by Slava, choosing the next prime following a random number
with a specified number of bits may give a number one more bit long.

diff --git a/basis/math/primes/primes.factor b/basis/math/primes/primes.factor
index 7e877a03ce3f9dfcd91fca9734c73ef0adb78260..27743a4a85780f45c2ee6006ab8da325d83c15b9 100644 (file)
--- a/basis/math/primes/primes.factor
+++ b/basis/math/primes/primes.factor
@@ -56,7 +56,8 @@ PRIVATE>
 : coprime? ( a b -- ? ) gcd nip 1 = ; foldable
 
 : random-prime ( numbits -- p )
-    random-bits* next-prime ;
+    [ ] [ 2^ ] [ random-bits* next-prime ] tri
+    2dup < [ 2drop random-prime ] [ 2nip ] if ;
 
 : estimated-primes ( m -- n )
     dup log / ; foldable