Recent questions tagged haskell

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haskell - repeatedly applying a function until the result is stable

I want to repeatedly apply a function simplify' until the result is "stable" (i.e. simplify'(x) == x): ... == expr then expr else simplify next See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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711 views

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haskell - Int vs Word in common use?

It seems like the common pattern of taking/returning Int (ie ByteString.hGet and Data.List.length) is contrary ... functions are partial on Int? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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695 views

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haskell - Simplifying a GADT with Uniplate

I'm trying to answer this stackoverflow question, using uniplate as I suggested, but the only solution I've ... this problem with uniplate? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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734 views

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haskell - What's the difference between Text.ParserCombinators.Parsec and Text.Parsec

Text Text.Parsec Text.Parsec.ByteString Text.Parsec.ByteString.Lazy Text.Parsec.Char Text.Parsec.Combinator Text.Parsec. ... Are they the same? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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897 views

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haskell - How to avoid recompiling in this cabal file?

I've been working on this Haskell project, and I have a cabal file for it. Now, my project is structured as a ... -dirs: src main-is: Main.hs See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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784 views

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haskell - How can I use GHCi with the new cabal 1.17 sandboxes?

I've been trying out cabal head which has support for sandboxes similar to cabal-dev. However there's not yet ... similar to cabal-dev ghci? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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583 views

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haskell - Combining Free types

I've been recently teaching myself about the Free monad from the free package, but I've come across a ... DSL was being debugged individually. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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687 views

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haskell - Automatic memoizing in functional programming languages

I always thought that Haskell would do some sort of automatic intelligent memoizing. E.g., the naive Fibonacci ... has done that already. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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829 views

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haskell - What happens to you if you break the monad laws?

Do the compiler or the more "native" parts of the libraries (IO or functions that have access to black magic ... expect you to be so careless? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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726 views

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haskell - Ambiguous type variable error msg

I don't think it is a bug, but I am a bit puzzled as to why that doesn't work. A bonus ... modules loaded: none. Prelude Control.Exception> See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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839 views

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haskell - "Illegal instance declaration" when declaring instance of IsString

I'm writing an application that uses UTF-16 strings, and to make use of the overloaded strings extension I ... there something I've missed? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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727 views

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haskell - Desugaring do-notation for Monads

As I'm learning Haskell I'm realizing that do notation is just syntatic sugar: a = do x <- [3..4] [1 ... Here's the source code the Undo plugin. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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632 views

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haskell - To what extent are Applicative/Monad instances uniquely determined?

As described this question/answers, Functor instances are uniquely determined, if they exists. For lists, there are ... not, an counter-example. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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697 views

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haskell - What monads can be expressed as Free over some functor?

The documentation for Free says: A number of common monads arise as free monads, Given data Empty a, Free ... expressible using Free and why? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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609 views

1 answer

haskell - What are skolems?

Eeek! GHCi found Skolems in my code! ... Couldn't match type `k0' with `b' because type variable ` ... escape (the ungrateful little blighters)? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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708 views

1 answer

haskell - What exactly does "effectful" mean

Time and again I read the term effectful, but I am still unable to give a clear definition of what it ... between effectful and with effects? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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622 views

1 answer

haskell - Neural Network Always Produces Same/Similar Outputs for Any Input

I have a problem where I am trying to create a neural network for Tic-Tac-Toe. However, for some reason, ... https://github.com/l33tnerd/hsann. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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659 views

1 answer

haskell - When is -XAllowAmbiguousTypes appropriate?

I've recently posted a question about syntactic-2.0 regarding the definition of share. I've had this ... all come straight from sugarSym. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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669 views

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haskell - What is Applicative Functor definition from the category theory POV?

I was able to map Functor's definition from category theory to Haskell's definition in the following way: ... formal and rigorous definition? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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855 views

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haskell - Left and Right Folding over an Infinite list

I have issues with the following passage from Learn You A Haskell (Great book imo, not dissing it): One big ... or am I missing something? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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897 views

1 answer

haskell - Parsec vs Yacc/Bison/Antlr: Why and when to use Parsec?

I'm new to Haskell and Parsec. After reading Chapter 16 Using Parsec of Real World Haskell, a question ... wasn't answered satisfactorily there. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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826 views

1 answer

haskell - Shorthand way for assigning a single field in a record, while copying the rest of the fields?

Let's say I have the following record ADT: data Foo = Bar { a :: Integer, b :: String, c :: String ... any less tedious ways of doing the same? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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625 views

1 answer

haskell - What's the status of current Functional Reactive Programming implementations?

I'm trying to visualize some simple automatic physical systems (such things as pendulum, robot arms,etc.) in ... , self-learning server process! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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793 views

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haskell - Creative uses of monads

I'm looking for creative uses of monads to learn from. I've read somewhere that monads have been used for ... usages. No standard monads please. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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819 views

1 answer

haskell - Do statement under a where clause

I'm trying to convert IO [String] to [String] with <- binding; however, I need to use a do block ... have some statements before the guards ? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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805 views

1 answer

haskell - Understanding lighting in OpenGL

I am trying to create a 3D sphere out of a bunch of triangles with Haskell / GLUT. It works quite nicely: The ... half z = realToFrac z / 2 See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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931 views

1 answer

haskell - Why is there no Show instance for functions?

Just a quick conceptual question, I am currently trying to learn and understand Haskell better. I know the Show ... command: print it Prelude> See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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1.1k views

1 answer

haskell - No instance for (Floating Int)

I am learning Haskell. I have created function which returns multiplication table up to 'n' in base 'b'. Numbers are ... (logBase b (n * n)) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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