How can I go through a list of numbers and compare it with an another list I am going through?

Question

I want to input two strings, "Hello" and "Hi" for example, and I want to go through every element in the two strings simultaneously and compare every character one by one. The two strings length in the actual program should be 5, if a char is equal to the other, return true, otherwise return false.

The program I have in mind should see 'H' in "Hello" and 'H' from "Hi" and return true, then I want it to check the 'e' in "Hello" and the 'i' in "Hi" and return false. I want it to keep on doing that till there is nothing to compare. I think I might need to use recursion but I am not sure how to implement it in this program really.

I tried using x:xs with the maximum range of 5 so [0..5], but it didn't work at all.

My code (not working):

uncurryingString :: String -> Int -> Char
uncurryingString a b = a !! b

match :: String -> String -> [Int] -> Bool 
match a b (x:xs)
            |   uncurryingString a [x+1 | x <- xs]  == uncurryingString b [x+1 | x <- xs]       = True
            |   otherwise                                                                       = False 

Answer 1

Using a list comprehension is often a good way to compute things in Haskell, but not in this particular case.

I could try this code:

 [a==b | a <- "Hello", b <- "Hi"]

What does this do? You might think that this returns True, because the 'H' letters match - or you might thing that this returns False, because the other letters don't match. In fact, it does both - in effect, it is running multiple nested loops.

[True,False,False,False,False,False,False,False,False,False]

So, the takeaway is to use list comprehensions when you want nested loops, or just working through one dataset. Here we just want a single loop that works through the two words in parallel. Hence it must be recursion.