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Today's Topics:
1. Data constraint? (Galaxy Being)
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Message: 1
Date: Thu, 3 Jun 2021 17:40:41 -0500
From: Galaxy Being <borg...@gmail.com>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <beginners@haskell.org>
Subject: [Haskell-beginners] Data constraint?
Message-ID:
<CAFAhFSV5PoH+4LvTve=jzgkcupe8j7pb6zazwhuzs3o60yg...@mail.gmail.com>
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If I have a type
type WaterChem = CaHardness NaturalChem | Alkalinity NaturalChem
and I want to have the values of CaHardness and Alkalinity constrained to
positive Int and between certain high and low values, I could do a newtype to
creater a NaturalChem number, thus never less than 0, but what is the best
practice to insure these values are between a certain range? Types in
Haskell can't go that far, can they? Reading this
<https://www.haskell.org/tutorial/moretypes.html> tells me I can have some
of what I want. How are type values that need to be constrained handled
best practices? Again, the type world of Haskell seems to do some of the
lifting, but I'd like some advice if I want to have both of my constraints.
--
⨽
Lawrence Bottorff
Grand Marais, MN, USA
borg...@gmail.com
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