[Haskell-beginners] Bool newtype

[Michael Alan Dorman]

Imants Cekusins <imantc at gmail.com> writes:

> for a Bool-like newtype:
>
> newtype B = B Bool
>
> , is there an easy way to use this newtype B in place of Bool?
>
> e.g.
>
> let b1 = B True
> in if b1 then 1 else 0
>
> ?

Imants,

You can create a function that converts a B to a Bool:

  toBool :: B -> Bool
  toBool B b = b

And then use the result of applying that function to your variable:

  let b1 = B True
  in if toBool b1
     then 1
     else 0

To do anything like this automatically would seem to me to defeat the
purpose of having distinct types, which is to clearly articulate what
values are appropriate in particular contexts.

Mike.