[Haskell-cafe] an idea for modifiyng data/newtype syntax: use `::=` instead of `=`

[Tom Ellis]

On Sat, Aug 08, 2015 at 11:02:27PM +0200, MigMit wrote:
> What you say is "if we don't use some perfectly legitimate language
> constructs and never use third-party code, than 'data' and 'newtype' are
> the same".

No, not at all.  I'm making a much stronger claim than that.  I'm claiming
the functionality provided by newtype is completely subsumed by that
provided by data.

> > On Sat, Aug 08, 2015 at 10:43:39PM +0200, MigMit wrote:
> >> Prelude> newtype A = A Int deriving Show
> >> Prelude> data B = B !Int deriving Show
> >> Prelude> let x = case x of A n -> A 1 in x
> >> A 1
> >> Prelude> let y = case y of B n -> B 1 in y
> >> *** Exception: <<loop>>
> > 
> > Sure, they're not exactly the same thing but if you get the translations
> > right you can use them for the same purposes:
> > 
> >    Prelude> let y = case y of b -> B 1 in y
> >    B 1
> > 
> > I list the translations here
> > 
> >    http://stackoverflow.com/questions/21327740/strict-single-constructor-single-field-data-declaration-vs-newtype/21331284#21331284