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Questions - deriving

Why automatical deriving for newtype does not work

I use library msgpack-types-0.0.4 and I have a type: newtype A = A Text and I tried deriving MessagePack, deriving newtype MessagePack, standalone derivings, it seems nothing works (or I do something...
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RandomB

haskell

deriving

Votes: 0

Answers: 0

Problem when deriving Eq from data type with function as field in Haskell

I'm trying to deriving Eq from data type with a function as a field but doesn't work as expected. I also try to write te instance but still doesn't work data Conf = Conf { rule :: ([Char] -> Ch...
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Javier Sánchez Castro

haskell

methods

functional-programming

equality

deriving

Votes: 0

Answers: 2

Latest Answer

What makes you think that this should be possible? If your type contains a function field, then comparing values of your type for equality is at least as difficult as comparing functions for equality....
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leftaroundabout

Can I use DerivingVia to derive instances for data types isomorphic to tuples

Given the following data type data Both a b = Both { left :: a, right :: b } I can write instances for Applicative etc. like so (omitting Functor here as we can use DeriveFunctor): instance Monoid a ...
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l7r7

haskell

deriving

derivingvia

Votes: 0

Answers: 2

Latest Answer

Inspired by this answer, and with the help of the generic-data package one can write: {-# LANGUAGE DeriveGeneric, DerivingStrategies, DerivingVia #-} import GHC.Generics import Generic.Data data Bot...
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l7r7

Alternative of Show that only uses name

Is there something like Show (deriving Show) that only uses an algebraic datatype's constructors? (please don't mind that I'm using the word constructor, I don't know the right name...) The reason for...
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John Smith

haskell

generics

deriving

Votes: 0

Answers: 3

Latest Answer

For a type with a Data.Data.Data instance, this function is easy: it's merely showConstr . toConstr :: Data a => a -> String For example, Prelude Data.Data> showConstr . toConstr $ Just 5 &q...
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amalloy

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