Set 15 Ex 7: avoid hexadecimal and octal

closes #29

exercises/Set15.hs

@@ -133,6 +133,9 @@ twoPersons name1 age1 employed1 name2 age2 employed2 = todo
 --
 -- Hint: remember readMaybe
 --
+-- PS. The tests won't test special cases of Int literals like hexadecimal
+-- (0x3a) or octal (0o14).
+--
 -- Examples:
 --  boolOrInt "True"    ==> Ok (Left True)
 --  boolOrInt "13"      ==> Ok (Right 13)

exercises/Set15Test.hs

@@ -149,7 +149,7 @@ sow (x:xs) (y:ys) = oneof [fmap (x:) $ sow xs (y:ys)
                           ,fmap (y:) $ sow (x:xs) ys]
 
 ex7_fail = forAll_ $ \(i::Int) ->
-  forAllBlind (choose ('a','z')) $ \c ->
+  forAllBlind (choose ('a','n')) $ \c -> -- don't generate 0o or 0x by accident
   forAllBlind (shuffle (c:show i)) $ \ni ->
   forAll_ $ \(b::Bool) ->
   forAllBlind (sow [c] (show b)) $ \nb ->