make the random word actually return a number in the full range of the input and replace division words with bitwise ones

basis/random/random-docs.factor

@@ -27,7 +27,13 @@ HELP: random
 
 HELP: random-bytes
 { $values { "n" "an integer" } { "byte-array" "a random integer" } }
-{ $description "Outputs an integer with n bytes worth of bits." } ;
+{ $description "Outputs an integer with n bytes worth of bits." }
+{ $examples 
+    { $unchecked-example "USING: prettyprint random ;"
+               "5 random-bytes ."
+               "B{ 135 50 185 119 240 }"
+    }
+} ;
 
 HELP: random-bits
 { $values { "n" "an integer" } { "r" "a random integer" } }

basis/random/random-tests.factor

@@ -1,4 +1,4 @@
-USING: random sequences tools.test kernel ;
+USING: random sequences tools.test kernel math math.functions ;
 IN: random.tests
 
 [ 4 ] [ 4 random-bytes length ] unit-test
@@ -9,3 +9,6 @@ IN: random.tests
 
 [ 2 ] [ V{ 10 20 30 } [ delete-random drop ] keep length ] unit-test
 [ V{ } [ delete-random drop ] keep length ] must-fail
+
+[ t ] [ 10000 [ 0 [ drop 187 random + ] reduce ] keep / 2 * 187 10 ~ ] unit-test
+[ t ] [ 10000 [ 0 [ drop 400 random + ] reduce ] keep / 2 * 400 10 ~ ] unit-test

basis/random/random.factor

@@ -2,7 +2,7 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: alien.c-types kernel math namespaces sequences
 io.backend io.binary combinators system vocabs.loader
-summary ;
+summary math.bitwise ;
 IN: random
 
 SYMBOL: system-random-generator
@@ -29,15 +29,17 @@ M: f random-32* ( obj -- * ) no-random-number-generator ;
 
 : random-bytes ( n -- byte-array )
     [
-        dup 4 rem zero? [ 1+ ] unless
+        dup 3 mask zero? [ 1+ ] unless
         random-generator get random-bytes*
     ] keep head ;
 
 : random ( seq -- elt )
     [ f ] [
         [
-            length dup log2 7 + 8 /i
-            random-bytes byte-array>bignum swap mod
+            length [
+                log2 8 + 8 /i
+                random-bytes byte-array>bignum
+            ] keep wrap
         ] keep nth
     ] if-empty ;