[Haskell-cafe] Unique Ordered Types

[Christopher Allen]

http://hackage.haskell.org/package/units is a pretty deep example of how to
have type-safe units.

On Wed, Aug 12, 2015 at 4:20 PM, Silvio Frischknecht <
silvio.frischi at gmail.com> wrote:

> Hi I'm experimenting with a unit system in haskell where users can add
> "base units". I want to reduce units after multiplication and bring it
> into a canonical form. The problem is what kind of types can the units
> have.
>
> 1)
>
> data UnitA
> data UnitB
>
> Problem: They can't be ordered so UnitA * UnitB can be compared to UnitB
> * UnitA, but I can't make a canonical form, which would make type
> inference a lot better.
>
> 2)
>
> type UnitA = Zero
> type UnitB = Suc Zero
>
> Problem: Now they can be ordered. But users can create conflicting
> "basic units"
>
>
>
> Silvio
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-- 
Chris Allen
Currently working on http://haskellbook.com
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