I'm on my phone which makes replying painful, but consider: data Weekday = Monday | Tuesday | Wednesday | Thursday | Friday data Shape = Circle Int | Rectangle Int Int Int Int | Triangle Int Int data Either a b = Left a | Right b Cheers, Alex On Sep 14, 2017 12:05 AM, "Anwar Ludin" wrote:

Hello everyone,

I have just started studying Haskell and I am having a hard time understanding type and value constructors.

So to create a new type, you write something like:

data FinancialInstrument = Financial String Double deriving (Eq, Show)

and then you can write:

ibm = Financial "ibm" 150

OK all good. This initializes a FinancialInstrument. What I don't quite grasp is what is the purpose of Financial (the data/value constructor)? And from what I have read, you could have also written:

data FinancialInstrument = FinancialInstrument String Double deriving (Eq, Show)

To me the second expression is a lot closer to the typical OOP way of doing things (where the type name and constructor(s) have the same name). Why would someone prefer the first notation?

Once a value has been constructed, how can I access its fields?

Is there a way to create values using named parameters?

Thanks!

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