CODEWITHSUNDEEP
haskellio
user3494699
user3494699

Reputation: 5

Haskell: Multiple Actions in Single Case

I am trying to get IO functions within Haskell to send a variable up the IO to use within the main of the program. The specific part below is the main part giving me grief.

getInformation :: Int -> [String] -> IO [String]
getInformation input db
    |input == 1 = return (inputOne db)
    |input == 2 = return (inputTwo db)
    |input == 3 = return (inputThree db)
    |input == 4 = return (inputFour db)
    |input == 5 = return (inputFive db)
    |input == 6 = return (inputSix db)
    |input == 7 = return (inputSeven db)
    |input == 8 = return (inputEight db)

inputOne ... inputEight all return a value of IO [String] and I am trying to have the return be based on [String] rather than IO [String]. Ideally I want to try something like this for each case but I'm not sure how to go about this:

db2 <- (inputOne db)
return (db2)

I have tried doing experiments along the lines of:

|input == 1 = {db2 <- (inputOne db)
               return (db2)}

However, this would error and not work even though I believe that is along the right lines.

Any help would be much appreciated.

Upvotes: 0

Views: 1001

Answers (1)

MathematicalOrchid
MathematicalOrchid

Reputation: 62808

If you want a do-block, you need the actual do keyword:

| input == 1 = do db2 <- inputOne db; return db2

You could also structure it like

| input == 1 = do
  db2 <- inputOut db
  return db2

if you prefer.

Notice that putting the result into a variable and immediately returning the same thing is the same as

| input == 1 = inputOne db

Upvotes: 3

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