[Haskell-cafe] clonetype

Wolfgang Jeltsch wolfgang-it at jeltsch.info
Wed Sep 26 12:41:29 UTC 2018

Am Dienstag, den 25.09.2018, 02:05 +0530 schrieb Harendra Kumar:
> That's where I started. I already use a newtype with GND for this, and
> it looks like this:
> newtype Count = Count Int64
>     deriving ( Eq
>              , Read
>              , Show
>              , Enum
>              , Bounded
>              , Num
>              , Real
>              , Integral
>              , Ord
>              )
> The problem is that most programmers are lazy or hard pressed for time
> and having to write a newtype with a big list of instances actually
> discourages the use of newtypes freely for this case, they may just
> make it a habit to let it go. We can't just deny this and say that
> programmers must be disciplined. They will often try taking the path
> of least effort.
I think that the time it takes to come up with and write down such
explicit lists is usually small compared to the time it takes to do all
the other development. And once you have made the instantiation lists
explicit, you will probably save time in the future, because bugs will
detected automatically more often. The latter point is something that is
often overlooked: people are under time pressure and strive for quick
solutions but spend more time in the long run this way.
All the best,
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