CODEWITHSUNDEEP
haskell
JSchwartz
JSchwartz

Reputation: 2724

How to express the following if-else if-else statement in Haskell?

I am trying to replicate the following requirements/code in Haskell

Pseudo-Code (the actual evaluations are much more complicated):

if (x == 1)
   doX()
else if (y == 1)
   doY()
else if (z == 1)
   doZ()
else
   doSomethingElse()

Right now I have this as WHEN statements for each, but that doesn't give me an ELSE, so I have

when (x == 1) $ do doX
when (y == 1) $ do doY
when (z == 1) $ do doZ

But then how do I manage my else?

Upvotes: 2

Views: 999

Answers (1)

bheklilr
bheklilr

Reputation: 54058

This looks like a good option for guards or a case statement. You could do something like

myAction :: Monad m => Int -> Int -> Int -> m ()
myAction x y z
    | x == 1 = doX
    | y == 1 = doY
    | z == 1 = doZ
    | otherwise = doSomethingElse

Or you can use the MultiWayIf extension:

myAction :: Monad m => m ()
myAction = do
    x <- getX
    y <- getY
    z <- getZ
    if | x == 1 -> doX
       | y == 1 -> doY
       | z == 1 -> doZ
       | otherwise -> doSomethingElse
    -- continue doing more stuff in myAction as needed

Upvotes: 5

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