Question

I can initialize the list of Int such beautiful way:

[2, 4 .. 20]

And I am just wondering if there is any to initialize the list of my datatype in such manner. Something like this, but using more haskell way:

data SieveElement = SieveElement { index :: Int,
                                   flag ::  Bool 
                                   } deriving (Show)

prepareSieve start end step
             | start > end = []
             | otherwise = [SieveElement start True] ++ (prepareSieve (start + step) end step)

let s = prepareSieve 2 20 2

Answer 1

How about using list comprehensions:

[SieveElement i True | i <- [2, 4 .. 20]]