CODEWITHSUNDEEP
stringlisthaskellchar
Elzine Burger
Elzine Burger

Reputation: 25

Is there a simple function to make a string of a list of chars?

I want to make a String from a list of chars [Lettre]

For example, ['1', '2', '3', 'W', '5', '5', 'W', '3'] should be printed as (1, 2, 3, W, 5, 5, W, 3)

Now, I use

data Lettre = Steen Char

makeString :: [Lettre] -> String
makeString [] = ""
makeString [Steen(x)] = x:[]
makeString (Steen(x):xs) = (x:", ") ++ makeString xs

but I feel like this could be easier.

Is there a simple function, something like toString? I tried using some functions I knew, but it doesn't seem to work on my code, so I keep using makeString.

A big thanks to anyone who could help me out :)

Upvotes: 0

Views: 156

Answers (1)

chepner
chepner

Reputation: 531265

Given a list of a characters, you could use intersperse, but that only allows single-character separators.

> "(" ++ intersperse ',' "123W55W3" ++ ")"
"(1,2,3,W,5,5,W,3)"

For a multicharacter separator like ", ", you can use intercalate, but then you need a list of String, not a list of Char.

The solution is to lift each character into a string, then use intercalate.

> "(" ++ intercalate ", " (map pure "123W55W3") ++ ")"
"(1, 2, 3, W, 5, 5, W, 3)"

I'm assuming the input is an actual [Char]/String value; if you actually have some more complicated Char wrapper, like

newtype Lettre = Steen Char

as could be inferred from your attempt, use instead something like

makeString :: [Lettre] -> String
makeString xs = "(" ++ intercalate ", " [[x] | Steen x <- xs] ++ ")"

Upvotes: 7

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