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    I'm relatively new to Haskell, and I'm trying to understand one of the definitions of HList. data instance HList '[] = HNil newtype instance HList ... with two fields) besides avoiding boxing of HCons1? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    This passage, which unfortunately lacks references, about the development of ADTs in Haskell, from A History of Haskell: Being Lazy With Class, section 5.1: ... wondering, how would such an ADT be useful? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I know only one prover that translates the algorithm that Quine gave for classical propositional logic in his book Methods of Logic (Harvard University ... published but not reproduced in this page. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I was experimenting with the singletons library and I found a case that I don't understand. {-# LANGUAGE GADTs, StandaloneDeriving, RankNTypes, ScopedTypeVariables, ... a1 (GHC.TypeLits.CmpNat a a1)))) See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm trying to wrap the Data.Binary.Put monad into another so that later I can ask it questions like "how many bytes it's going to write" or "what ... : There is also a second part to this question here. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I have used writeBS writeText from Snap and renderTemplate from heist but none of them seems to support unicode. site :: Snap () site = do ifTop (writeBS ... in fact its output is just some messy code. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    using cabal; came accross this error. did cabal install and this happened. failed during the building phase. The exception was: ExitFailure 1 checked ... Glasgow Haskell Compilation version: 7.8.4 See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I did: cabal update cabal install gtk2hs-buildtools But stuck here: >cabal install gtk Resolving dependencies... [1 of 2] Compiling SetupWrapper ( C: ... ghc-pkg uregister. Now see th updated answer. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Is there a benefit to specifically reserving varied data-type pairings for tuples like such: [(23, "Jordan"), (8, "Bryant")] As opposed to just using ... the second piece of code will not work in Haskell See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm having trouble installing the Haskell framework Snap on macOS Sierra. Whenever I install it, I get the following message: Resolving dependencies... ... using sudo and deleting my ~/.ghc file See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Everything was working great up until about a month or so ago... Suddenly I'm getting berkson.github.io/source/blog.hs: 333, 42 ? Couldn't ... com/berkson/berkson.github.io/blob/source/source/blog.hs#L330 See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I've got the following, which type-checks: p_int = liftA read (many (char ' ') *> many1 digit <* many (char ' ')) Now, as the function name ... pairs in proteins. I have no control over the file format!) See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm getting an error for this code, and I don't understand where the conflict is. {-# LANGUAGE TypeFamilies, FlexibleContexts, FlexibleInstances, ... hs:29:8 Failed, modules loaded: none. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'd like something like the following: constrName :: Data a=> a -> String constrName = showConstr . toConstr But for GHC.Generics. I see the Constructor class, but ... in scope. I'm using base-4.8.1.0. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    As in my previous question, I'm trying to wrap the Data.Binary.Put monad into another monad so that later I can ask it questions like "how many ... infinite loop :-|. Could someone please help further? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I am lazily encoding lists using this code (taken from this SO question): import Data.Binary newtype Stream a = Stream { unstream :: [a] } instance Binary a ... this not lazy, and how I can make it lazy? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm working on this tool where the user can define-and-include in [config files | content text-files | etc] their own "templates" (like mustache etc) and ... results for "how to loop in Haskell" etc..) See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Something that should be easy but somehow I don't find how to do it... let's have the following string: "[email protected]_command-7a86cb8b-0987-fe40-61f2- ... ","-7a86cb8b-0987-fe40-61f2-42b0f6fc3e1c"]... See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I would like to embed ReaderT into another monad transformer. How do I do this? The example below uses Scotty but I think it would be the same with ... Actual type: ScottyT Text (ReaderT Config IO) () See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Learning Haskell, in ghci: Prelude Data.Ratio> :type 0.15 0.15 :: Fractional a => a Prelude Data.Ratio> 0.15 0.15 it :: Double Why are ... ? Are those two instances of 0.15 actually different types? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I am a new learner of Haskell, my code is as follows: data Num a=>Units a = Units a (SymbolicManip a ) deriving (Eq) I am not sure how to fix it? Anyone can help 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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    data A=A data B=B data AB=A|B Which makes a sum type AB from A and B. but the last line induces a compile error "multiple declarations of ... ghc disallows me from making sum types for user-defined types? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Trying to use hmatrix, to create a zero marix. For some reason, when I try this on command line, it works: buildMatrix 2 3 ((r,c) -> fromIntegral 0) However ... -> ...); m } Failed, modules loaded: none. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Being quite new to Haskell, I'm currently trying to improve my skills by writing an interpreter for a simple imperative toy language. One of the expressions in this ... with IO I see no way out of that..? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I am following along with the Learn you a Haskell for great good, I have implemented take': take' :: (Ord i, Num i) => i -> [a] -> [a] take' n _ | n <= 0 = [] ... [a] -> [a]), Ord i) => i -> [a] -> [a] See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm running on a container with 768MB ram and 512 MB swap space. I can't increase either of this. cabal install criterion always gives Failed during the ... this or do I have to make do without criterion? See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    Problem: using fold, take from the list elements which are on the even positions: GHCi> evenOnly [1..10] [2,4,6,8,10] GHCi> evenOnly ['a'.. ... idea is correct, I just did something wrong with the syntax. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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    I'm currently writing some pipes-core/attoparsec plumbing for a small project of mine. I want each parser to give a pipe that awaits ByteString input ... or even be equivalent to the fourth one. See Question&Answers more detail:os...
asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)
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