2016 Update

Task/Gray-code/Forth/gray-code.fth

@@ -1,21 +1,21 @@
-: >gray ( n -- n ) dup 2/ xor ;
-
+: >gray ( n -- n' ) dup 2/ xor ;   \ n' = n xor (n logically right shifted 1 time)
+                                               \ 2/ is Forth divide by 2, ie: shift right 1
 : gray> ( n -- n )
-  0  1 31 lshift  ( g b mask )
+  0  1 31 lshift  ( -- g b mask )
   begin
-    >r
+    >r                                        \ save a copy of mask on return stack
      2dup 2/ xor
      r@ and or
-    r> 1 rshift
-    dup 0=
+     r> 1 rshift
+     dup 0=
   until
-  drop nip ;
+  drop nip ;                                  \ clean the parameter stack leaving result only
 
 : test
-  2 base !
+  2 base !                                    \ set system number base to 2. ie: Binary
   32 0 do
-    cr i  dup 5 .r ."  ==> "
+    cr I  dup 5 .r ."  ==> "                  \ print numbers (binary) right justified 5 places
     >gray dup 5 .r ."  ==> "
     gray>     5 .r
   loop
-  decimal ;
+  decimal ;                                   \ revert to BASE 10