Hi, Am Mittwoch, dem 30.11.2022 um 16:21 +0100 schrieb Henning Thielemann:

...

I want to create a list of each values in order to create meaningfull error message for the user and simplify my Arbitrary instances.

deriving (Enum, Bounded)

then use [minBound .. maxBound]

if you want to golf it a bit more, then [minBound..] works as well. (I vaguely remember that there was a variant that didn’t even need Bounded, just, but I don’t recall it right now. Maybe it was [toEnum 0..]? but that only works for certain instances.) Cheers, Joachim -- Joachim Breitner mail@joachim-breitner.de http://www.joachim-breitner.de/

Hi, Am Samstag, dem 03.12.2022 um 20:12 +0100 schrieb Henning Thielemann:

...

if you want to golf it a bit more, then

   [minBound..]

works as well.

Wouldn't this create an infinite tail of undefined value

That’s what I thought until I learned about this. Anyways, ghci says it doesn’t: ghci> [False .. ] [False,True] ghci> [LT .. ] [LT,EQ,GT] [x..] is just enumFrom x, and the docs for Enum says

enumFrom and enumFromThen should be defined with an implicit bound,

https://hackage.haskell.org/package/base-4.17.0.0/docs/Prelude.html#t:Enum Cheers, Joachim -- Joachim Breitner mail@joachim-breitner.de http://www.joachim-breitner.de/

Also, you can simplify the "map pure (...)" by using `elements` :) https://hackage.haskell.org/package/QuickCheck-2.14.2/docs/Test-QuickCheck.h... On Wed, Nov 30, 2022 at 5:23 PM Brandon Allbery wrote:

Derive Enum and Bounded and use [minBound .. maxBound] :: [InputType]

On Wed, Nov 30, 2022 at 10:19 AM PICCA Frederic-Emmanuel wrote:

...

Hello, I have a type like this

data InputType = CristalK6C | MarsFlyscan | MarsSbs | SixsFlyMedH | SixsFlyMedV | SixsFlyMedVEiger | SixsFlyMedVS70 | SixsFlyScanUhv | SixsFlyScanUhv2 | SixsFlyScanUhvTest | SixsFlyScanUhvUfxc | SixsSbsFixedDetector | SixsSbsMedH | SixsSbsMedV | SixsSbsMedVFixDetector deriving (Eq, Show)

I want to create a list of each values in order to create meaningfull error message for the user and simplify my Arbitrary instances. I do not want to type two time the values.

instance Arbitrary InputType where arbitrary = oneof (map pure [ CristalK6C , MarsFlyscan , MarsSbs , SixsFlyMedH , SixsFlyMedV , SixsFlyMedVEiger , SixsFlyMedVS70 , SixsFlyScanUhv , SixsFlyScanUhv2 , SixsFlyScanUhvTest , SixsFlyScanUhvUfxc , SixsSbsFixedDetector , SixsSbsMedH , SixsSbsMedV , SixsSbsMedVFixDetector ] )

Thanks for your help

Frederic _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

-- brandon s allbery kf8nh allbery.b@gmail.com _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

Also, you can simplify the "map pure (...)" by using `elements` :)

thanks another question I have plenty of instance build like this instance Arbitrary TypeA where arbitrary = TypeA <$> arbitrary <*> arbitrary ... <*> arbitrary is there a convenient way to avoid typing this it seems purely mechanical thanks Fred

uncurry TypeA <$> arbitrary uncurry3 TypeA <$> arbitrary

would be a bit shorter if this is important.

I think that writing less line is better and less error prone. thanks again Frederic