Hi Jocob
I would recommend you to go through the LYH (
http://learnyouahaskell.com/making-our-own-types-and-typeclasses ) .
data Either a b = Left a | Right b deriving (Eq, Ord, Read, Show)
Lets say you have a division function and you want to avoid division by
zero so this simple function
simpleDiv :: Int -> Int -> Int
simpleDiv m n = div m n
will through error and stop executing rest of you code ( See more on error
handling ) so you can write your function which can handle this
division :: Int -> Int -> Either String Int
division m n
| n == 0 = Left "Division by zero"
| otherwise = Right $ div m n
You can extend this solution as you wish and lets say you want both , some
times integer division and some times floating point division based on
flag. You set you flag true for floating division and false for integer
division.
data Either' a b c = Left a | Mid b | Right c deriving ( Show , Eq )
tempFunction :: Int -> Int -> Bool -> EIther' String Double Int
tempFunction m n f
| n == 0 = Left "Division by zero"
| f = Mid $ m / n
| otherwise = Right $ div m n
I haven't tested this code but the idea is if you want to return different
results then you use this. Also see Use of Either (
http://book.realworldhaskell.org/read/error-handling.html ). Hopefully I
have explained it correctly.
--Mukesh
On Thu, Feb 7, 2013 at 8:07 AM, Jacob Thomas
Hello
I'm new to Haskell, and need help with figuring out the Either type... Any example to show how this works?
Jacob
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