Recent questions tagged Haskell

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This is just a hypothetical scenario to illustrate my question. Suppose that there are two threads and one TVar ... in an inconsistent state? See Question&Answers more detail:os...

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

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haskell - Type inference with GADTs - a0 is untouchable

Lets say I have this program {-# LANGUAGE GADTs #-} data My a where A :: Int -> My Int B :: Char ... determine the type. Please enlighten me :) See Question&Answers more detail:os...

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

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haskell - Is there a way to generalize this TrieMap code?

Below is a simple Haskell program which computes equalities on trees: import Control.Monad import Control.Applicative ... the differences away. See Question&Answers more detail:os...

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

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997 views

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haskell - GHC rewrite rule specialising a function for a type class

Using the GHC RULES pragma, it is possible to specialise a polymorphic function for specific types. Example ... type class-based specialisation? See Question&Answers more detail:os...

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

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877 views

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haskell - Can reactive-banana handle cycles in the network?

We have code like this: guiState :: Discrete GuiState guiState = stepperD (GuiState []) $ union (mkGuiState < ... works fine. Any suggestions? See Question&Answers more detail:os...

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

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haskell - Testing with HTF

There's an incredible lack of decent documentation on HTF. All I could find was a Tutorial which doesn't ... and modules structure, cabal)? See Question&Answers more detail:os...

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

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haskell - Modulus/Remainder function for non-integers

rem gives this: Prelude> rem 9 8 1 I wanted something like this: Prelude> nonIntRem 9.1 8 1.0999999999999996 I ... 'd like to know about it. See Question&Answers more detail:os...

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

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haskell - How to type cast

C#: static int F(object x) { return x is string ? 1 : 2; } Haskell? The tricky bit seems to me that ... an object is a Customer or an Order. See Question&Answers more detail:os...

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

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haskell - Is there a better way to express the absolute error function in point-free notation?

In pointful notation: absoluteError x y = abs (x-y) An unclear example in pointfree notation: absoluteError' = curry (abs . uncurry (-)) See Question&Answers more detail:os...

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

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haskell - How to find out GHC's memory representations of data types?

Recently, blog entries such as Computing the Size of a Hashmap explained how to reason about space complexities of ... in the right direction? See Question&Answers more detail:os...

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

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1.5k views

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haskell - No output will be generated because there is no Main module

I wrote a simple module called Test: module Test (main) where main = putStrLn "Hello" However, when i try ... because there is no Main module. See Question&Answers more detail:os...

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

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haskell - Are there contravariant monads?

Functors can be covariant and contravariant. Can this covariant/contravariant duality also be applied to monads? ... sense? Any examples? See Question&Answers more detail:os...

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

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haskell - Why does foldr use a helper function?

In explaining foldr to Haskell newbies, the canonical definition is foldr :: (a -> b -> b) -> b ... how this definition would improve inlining. See Question&Answers more detail:os...

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

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haskell - How to use hsc2hs to bind to constants, functions and data structures?

i need a example how to use hsc2hs, i thought that when i write a header file like: // foo.h #define PI 3 ... who can give me a better 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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973 views

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haskell - What does uncurry ($) do?

I'm doing some excersises where I have to add a function's type and explain what it does. I'm stuck with ... really have no idea what it does. See Question&Answers more detail:os...

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

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1.2k views

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haskell - What does uncurry ($) do?

I'm doing some excersises where I have to add a function's type and explain what it does. I'm stuck with ... really have no idea what it does. See Question&Answers more detail:os...

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

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1.1k views

1 answer

haskell - How to use hsc2hs to bind to constants, functions and data structures?

i need a example how to use hsc2hs, i thought that when i write a header file like: // foo.h #define PI 3 ... who can give me a better 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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947 views

1 answer

haskell - What does uncurry ($) do?

I'm doing some excersises where I have to add a function's type and explain what it does. I'm stuck with ... really have no idea what it does. See Question&Answers more detail:os...

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

0 votes

1.1k views

1 answer

haskell - How to use hsc2hs to bind to constants, functions and data structures?

i need a example how to use hsc2hs, i thought that when i write a header file like: // foo.h #define PI 3 ... who can give me a better example? See Question&Answers more detail:os...

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

0 votes

1.0k views

1 answer

haskell - What does uncurry ($) do?

I'm doing some excersises where I have to add a function's type and explain what it does. I'm stuck with ... really have no idea what it does. See Question&Answers more detail:os...

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

0 votes

1.0k views

1 answer

haskell - How to use hsc2hs to bind to constants, functions and data structures?

i need a example how to use hsc2hs, i thought that when i write a header file like: // foo.h #define PI 3 ... who can give me a better example? See Question&Answers more detail:os...

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

0 votes

1.1k views

1 answer

haskell - What does uncurry ($) do?

I'm doing some excersises where I have to add a function's type and explain what it does. I'm stuck with ... really have no idea what it does. See Question&Answers more detail:os...

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

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1.1k views

1 answer

haskell - What advantages do StableNames have over reallyUnsafePtrEquality#, and vice versa?

data StableName a Stable names have the following property: If sn1 :: StableName and sn2 :: ... StableNames over reallyUnsafePtrEquality#? See Question&Answers more detail:os...

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

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1.3k views

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haskell - Parsec.Expr repeated Prefix/Postfix operator not supported

The documentation for Parsec.Expr.buildExpressionParser says: Prefix and postfix operators of the same precedence can ... for a better solution See Question&Answers more detail:os...

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

0 votes

1.2k views

1 answer

haskell - Using a Lens to read multiple fields

Given the types data Prisoner = P { _name :: String , _rank :: Int , _cereal :: Cereal } data Cereal = C { _number : ... s b -> Getter s (a,b)? See Question&Answers more detail:os...

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

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1.4k views

1 answer

haskell - Convert a String list to an Int list

I've got a list of strings, is it possible to convert it to an list of ints? E.g.: ["1","2"] -> [1,2] See Question&Answers more detail:os...

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

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1.1k views

1 answer

haskell - How to tell if a list is infinite?

Is there a way to tell if a list in Haskell is infinite? The reason is that I don't want to apply functions such as length to infinite lists. See Question&Answers more detail:os...

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

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1.1k views

1 answer

haskell - Load pure global variable from file

I have a file with some data in it. This data never changes and I want to make it available ... of unsafePerformIO? Are there alternatives? See Question&Answers more detail:os...

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

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