CODEWITHSUNDEEP
stringlisthaskell
Dodande
Dodande

Reputation: 99

How to add new string element to a list of strings?

In my homework, I want to write a function which adds a string to a list of strings, but I have no idea how to do it.

I thought it would be something like this:

AddToLS :: [String] -> String -> [String]
AddToLS ls s = (ls : s)

But this code doesn't even compile.

It should work like this:

AddToLS [] "one" =["one"]
AddToLS ["one"] "two" =["one","two"]
AddToLS ["one","two"] "there" =["one","two","there"]

Upvotes: 3

Views: 349

Answers (1)

developer_hatch
developer_hatch

Reputation: 16224

You want to add an element of type string at the end, so, you can concat that element wrapped into a list and use the existing (++) function:

(++) :: [a] -> [a] -> [a]

so you will have to take your element and put it inside a list, like this:

AddToLS ["one", "two"] "three"

will be:

["one", "two"] ++ ["three"]

but you can define your own concat only for list of strings, as I can see, the arguments are flipped:

AddToLS :: [String] -> String -> [String]
addToLS = flip $ (++) . (:[])

that's equivalent to:

AddToLS :: [String] -> String -> [String]
addToLS ss s = ss ++ [s]

Upvotes: 5

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