typeclass

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Haskell: Possible fix: add (Eq a) to the context of

I\'m kind of new to Haskell and I\'m having a hard time understanding what is wrong with my code here.[详细]

2023-02-10 13:50 分类：问答
Why does type inference chooses only most specific type of the target reference when looking at implicit conversions?

Consider the following simple code to create a typesafe equals. This first section allows me to create an Identity typeclass for any type.[详细]

2023-02-09 13:15 分类：问答
Making (a, a) a Functor

How can I make (a, a) a Functor without resorting to a newtype? Basically I want it to work like this:[详细]

2023-02-07 12:20 分类：问答
Why does Numeric behave differently than Ordered?

Scala has a number of traits that you can use as type classes, for example Ordered and Numeric in the package scala.math.[详细]

2023-02-07 00:17 分类：问答
How do you use the Bounded typeclass in Haskell to define a type with a floating point range?

I expected the following code to fail with a type error due to violation of the minBound and maxBound. But, as you can see, it goes through without flagging an error.[详细]

2023-02-01 11:43 分类：问答
Instantiate type variable in Haskell

EDIT: Solved. I was unware that enabling a language extension in the source file did not enable the language extension in GHCi. The solution was to :set FlexibleContexts in GHCi.[详细]

2023-01-31 18:45 分类：问答
Haskell overlapping instances and type functions

I have the following typeclass which models a SQL-like query optimization: class OptimizableQuery q where[详细]

2023-01-31 03:54 分类：问答
Looking for example of type class usage that will work in Scala 2.7.7 and 2.8 scripts

Hi I\'m looking for a quick example of type class usage in Scala that will work in both 2.7.7 and 2.8 environments.[详细]

2023-01-30 01:26 分类：问答
Haskell typeclasses and C++ template classes

Is it possible to emulate the type class functionality of Haskell with C++ (or C#) templates? Does it make sense or is there any payoff in doing that?[详细]

2023-01-29 17:52 分类：问答
Adding a validity check dependent on a typeclass (Optional implicits)

In scala, we can use implicit typeclasses to conditionally add methods onto a parameterized type dependent on that type\'s parameters. For example, Iterator.sum:[详细]

2023-01-29 14:32 分类：问答