cetin tozkoparan
sublist :: Eq a => [a] -> [a] -> Bool sublist [] _ = True sublist (_:_) [] = False
This can be simplified a bit, I think (Reformatted to one line):
sublist (x:xs) (y:ys) | x == y = if isEqual (x:xs) (y:ys) == False then sublist (x:xs) ys else True
I don't like the "== False" for boolean expressions, so I'd write: sublist (x:xs) (y:ys) | x == y = if not (isEqual (x:xs) (y:ys)) then sublist (x:xs) ys else True Or, swithing then and else clauses: sublist (x:xs) (y:ys) | x == y = if isEqual (x:xs) (y:ys) then True else sublist (x:xs) ys If you look at the following clause:
| otherwise = sublist (x:xs) ys
you'll notice that it is the same as the "else" clause. We can therefore write: sublist (x:xs) (y:ys) | x == y && isEqual (x:xs) (y:ys) = True | otherwise = sublist (x:xs) ys isEqual will re-test x==y, so this is redundant: sublist (x:xs) (y:ys) | isEqual (x:xs) (y:ys) = True | otherwise = sublist (x:xs) ys The pattern guard is a bit gratuitious, why not write: sublist (x:xs) (y:ys) = isEqual (x:xs) (y:ys) || sublist (x:xs) ys Which is how you'd define the problem: a list xs is a sublist of ys if they have equal prefixes, or if xs is a sublist of the tail of ys.
isEqual :: Eq a => [a] -> [a] -> Bool
Slightly misleading name, since it checks a prefix, not complete equality.
isEqual [] _ = True isEqual (_:_) [] = False isEqual (x:xs) (y:ys) | x==y = isEqual xs ys | otherwise = False
Similar to the above, you could write: isEqual (x:xs) (y:ys) = x == y && isEqual xs ys "lists (x:xs) and (y:ys) 'isEqual' if x == y and xs 'isEqual' ys" As pointed out, you could (and should) write this using a couple of Prelude functions. Oh, any errors in the code are left as excercises for the reader (in other words, I didn't test this code at all, but don't want to be perceived as lazy.) -k -- If I haven't seen further, it is by standing in the footprints of giants