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Re: Nested "Maybe"

From Paul Rubin <no.email@nospam.invalid>
Newsgroups comp.lang.haskell
Subject Re: Nested "Maybe"
Date 2021-04-09 14:27 -0700
Organization A noiseless patient Spider
Message-ID <877dlb87yn.fsf@nightsong.com> (permalink)
References <878s5rtb4g.fsf@bsb.me.uk> <87blan883u.fsf@nightsong.com>

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Paul Rubin <no.email@nospam.invalid> writes:
> data Precision a = Roughly a | Exactly a
> data Approximate a = Maybe (Precision a)

Alternatively maybe you want an actual 3-way Maybe, e.g.

data Approximate a = Invalid | Roughly a | Exactly a

and then you could write typeclass instances (monad, monoid, etc.)
analogously with Maybe.

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Thread

Nested "Maybe" Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-04-09 22:13 +0100
  Re: Nested "Maybe" Paul Rubin <no.email@nospam.invalid> - 2021-04-09 14:24 -0700
    Re: Nested "Maybe" Paul Rubin <no.email@nospam.invalid> - 2021-04-09 14:27 -0700
  Re: Nested "Maybe" Mark Carroll <mtbc@bcs.org> - 2021-04-09 17:33 -0400

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