movex [] a s = []
movex (x:xs) a s
| elem a x = moveNow x a s
| otherwise = x : (movex xs a s)
where
moveNow x a s
| s == 'l' = moveNow2 x a
where
moveNow2 [] _ = []
moveNow2 (x:y:xs) a
| x == ' ' && y == a = a : x : moveNow2 (y:xs) a
| otherwise = x : moveNow2 (y:xs) a
<- This is what I got right now
I am trying to make a function that iterates through [string], finds the right string and then mutates it.
given input
func ["abc", "dfg"] f l -- move f in this list 1 space left --
expected output
["abc", "fdg"]
Right now I am stuck at movex function that gives me error
Couldn't match expected type `Char' with actual type `[Char]'
In the first argument of `(:)', namely `x'
In the expression: x : (movex xs a s)
Direct solution to the error is to replace the line
| elem a x = moveNow x a s
With
| elem a x = moveNow x a s : movex xs a s
Or, probably
| elem a x = moveNow x a s : xs
Depending on what you want to do after the first match: continue looking for certain character, or leave other strings untouched.
Your moveNow
function has return type String
, or [Char]
, while movex
has [String]
, or [[Char]]
, that's why compiler complains.
To avoid such problems(or fix them easier) consider writing explicit type signatures, like so:
movex :: [String]->String->String->[String]
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