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I totally understand your frustration with Haskell. I understand the tutorials and have read though the books available, but when I try to use the language on

by todd8 9y ago

I totally understand your frustration with Haskell. I understand the tutorials and have read though the books available, but when I try to use the language on a small real project, say a 2d barcode generator, I have trouble getting off the ground. Its not even clear to me which set of features are recommended for the language. It seems like different users program in different, incompatible, languages! Here is a list of optional language extensions supported by GHC: Cpp OverlappingInstances UndecidableInstances IncoherentInstances UndecidableSuperClasses MonomorphismRestriction MonoPatBinds MonoLocalBinds RelaxedPolyRec ExtendedDefaultRules ForeignFunctionInterface UnliftedFFITypes InterruptibleFFI CApiFFI GHCForeignImportPrim JavaScriptFFI ParallelArrays Arrows TemplateHaskell TemplateHaskellQuotes QuasiQuotes ImplicitParams ImplicitPrelude ScopedTypeVariables AllowAmbiguousTypes UnboxedTuples UnboxedSums BangPatterns TypeFamilies TypeFamilyDependencies TypeInType OverloadedStrings OverloadedLists NumDecimals DisambiguateRecordFields RecordWildCards RecordPuns ViewPatterns GADTs GADTSyntax NPlusKPatterns DoAndIfThenElse RebindableSyntax ConstraintKinds PolyKinds DataKinds InstanceSigs ApplicativeDo StandaloneDeriving DeriveDataTypeable AutoDeriveTypeable DeriveFunctor DeriveTraversable DeriveFoldable DeriveGeneric DefaultSignatures DeriveAnyClass DeriveLift DerivingStrategies TypeSynonymInstances FlexibleContexts FlexibleInstances ConstrainedClassMethods MultiParamTypeClasses NullaryTypeClasses FunctionalDependencies UnicodeSyntax ExistentialQuantification MagicHash EmptyDataDecls KindSignatures RoleAnnotations ParallelListComp TransformListComp MonadComprehensions GeneralizedNewtypeDeriving RecursiveDo PostfixOperators TupleSections PatternGuards LiberalTypeSynonyms RankNTypes ImpredicativeTypes TypeOperators ExplicitNamespaces PackageImports ExplicitForAll AlternativeLayoutRule AlternativeLayoutRuleTransitional DatatypeContexts NondecreasingIndentation RelaxedLayout TraditionalRecordSyntax LambdaCase MultiWayIf BinaryLiterals NegativeLiterals DuplicateRecordFields OverloadedLabels EmptyCase PatternSynonyms PartialTypeSignatures NamedWildCards StaticPointers TypeApplications Strict StrictData MonadFailDesugaring I've seen different subsets of these extensions recommended. Is there some canonical subset recommended by anyone doing real work in Haskell? Even more off topic: in reference to your note about the word "stubbornness", the word "bookkeeping" has three consecutive doubled letters. I believe that there are no examples of four consecutive doubled letters in any ordinary English dictionary, but I ought to grep the longer lexicons I've got at home.

tome 9y ago
> It seems like different users program in different, incompatible, languages! None of them are incompatible as far as I am aware. If they are, I'm sure it's in very minor ways that don't occur in practice.
- todd8 9y ago
  I'm sorry, I don't understand or maybe I wasn't clear. These extensions change the meanings (semantics and syntax) of Haskell programs accepted by the compiler. A program which would normally terminate using Haskell's ordinary lazy semantics might not terminate when using the Strict extension that changes the default semantics to less lazy. As far as I can tell from blogs like [1], the other language extensions also change the language in ways that are not forward and backward compatible with out-of-the-box Haskell. [1] https://ocharles.org.uk/blog/ https://ocharles.org.uk/blog/
  - tome 9y ago
    You were perfectly clear, but just mostly incorrect, I think. You are correct that Strict is a language extension that significantly changes the semantics of a Haskell program. It's a new extension so it didn't cross my mind. But besides Strict the number of extensions that change semantics of existing programs in a significant but non-forward and -backward compatible way is very, very small. Basically, the summary of Haskell extensions is: Around half of them are new features that should be in the language standard but aren't because a new standard hasn't been produced for years. Around half of them extend (not change) the language in powerful ways and are best avoided unless you really need them. Around Ɛ% are things that significantly change the semantics, and 0% are things that mean you're programming in a "different, incompatible, language" (all extensions are compatible across module boundaries).
    - todd8 9y ago
      Thanks, I won't give up on Haskell yet. You make a good point that should have been obvious to me: the extensions are confined to the module boundaries.

by todd8 9y ago

tome 9y ago

> It seems like different users program in different, incompatible, languages! None of them are incompatible as far as I am aware. If they are, I'm sure it's in very minor ways that don't occur in practice.

todd8 9y ago
I'm sorry, I don't understand or maybe I wasn't clear. These extensions change the meanings (semantics and syntax) of Haskell programs accepted by the compiler. A program which would normally terminate using Haskell's ordinary lazy semantics might not terminate when using the Strict extension that changes the default semantics to less lazy. As far as I can tell from blogs like [1], the other language extensions also change the language in ways that are not forward and backward compatible with out-of-the-box Haskell. [1] https://ocharles.org.uk/blog/ https://ocharles.org.uk/blog/
- tome 9y ago
  You were perfectly clear, but just mostly incorrect, I think. You are correct that Strict is a language extension that significantly changes the semantics of a Haskell program. It's a new extension so it didn't cross my mind. But besides Strict the number of extensions that change semantics of existing programs in a significant but non-forward and -backward compatible way is very, very small. Basically, the summary of Haskell extensions is: Around half of them are new features that should be in the language standard but aren't because a new standard hasn't been produced for years. Around half of them extend (not change) the language in powerful ways and are best avoided unless you really need them. Around Ɛ% are things that significantly change the semantics, and 0% are things that mean you're programming in a "different, incompatible, language" (all extensions are compatible across module boundaries).
  - todd8 9y ago
    Thanks, I won't give up on Haskell yet. You make a good point that should have been obvious to me: the extensions are confined to the module boundaries.