Hi Josh! dhall already provides FromDhall instances for Set and HashSet, which fail when the input Dhall list contains duplicates. Adding instances for e.g. Word8 that would fail when the source Natural is greater than 255 doesn't seem like a stretch. Please do open an issue at https://github.com/dhall-lang/dhall-haskell/issues so we can discuss the idea with the other maintainers. Cheers, Simon Am Mi., 19. Aug. 2020 um 08:56 Uhr schrieb ☂Josh Chia (謝任中) :

Correction to my original message: No problems for Double, which already has a FromDhall instance, but I'm trying to solve the problem for Word8, Word16 & Word32.

Interestingly, Word8, Word16 & Word32 have ToDhall instances but no FromDhall instances.

On Wed, Aug 19, 2020 at 2:50 PM ☂Josh Chia (謝任中) wrote:

...

Hi,

Let's say I have a record type: data Foo = Foo { v :: Word16 }

I want to have a FromDhall instance for Foo. I know this is easy to do if v is Integer instead of Word16. But v is Word16. Does Dhall enable the user to cleanly express how to input a Word16 with the requisite range checks, or is the user expected to only use Integer and do his own conversion and range checks within Haskell after inputting the Integer from Dhall? I have a record with Word32, Word16, Word8 & Double fields instead of Integer & Scientific.

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