July 2023 - Libraries

[ANN] BNFC 2.9.5 released
by Andreas Abel 26 Jul '23

26 Jul '23

BNFC 2.9.5 is available at - https://hackage.haskell.org/package/BNFC-2.9.5 - https://github.com/BNFC/bnfc/releases/tag/v2.9.5 (binaries and changelog) Feedback welcome, problems at https://github.com/BNFC/bnfc/issues . The BNF Converter (bnfc) is a wizard generating syntax trees, parser and printer from a Labelled BNF (LBNF) grammar. It is currently able to generate Haskell, Agda, C, C++, Java, and OCaml representations. Supported parser generators: Happy, ocamlyacc, Menhir, ANTLR, CUP, Bison. More information: http://bnfc.digitalgrammars.com Changes in 2.9.5: * C/C++/Java: escape newline etc. when printing `String` and `Char` literals [[#449](https://github.com/BNFC/bnfc/issues/449)] * Java/ANTLR: unescape `String` and `Char` literals in parser (needs Java ≥ 15) [[#451](https://github.com/BNFC/bnfc/issues/451)] * Java/ANTLR: fix case problem with language names like `C` [[#455](https://github.com/BNFC/bnfc/issues/455)] * Java with line numbers: compatibility with `jflex` ≥ 1.8 [[#453](https://github.com/BNFC/bnfc/issues/453)] * Haskell/GADT: generated `ComposOp.hs` no longer needs `mtl` library [[#438](https://github.com/BNFC/bnfc/pull/438)] * Ocaml: fixed a crash in printer with unbalanced `}` [[#439](https://github.com/BNFC/bnfc/issues/439)] * Ocaml: lex escape sequences in `Char` [[#452](https://github.com/BNFC/bnfc/issues/452)] * Ocaml: removed superfluous `let rec` in the printers for token categories Cheers, Andreas -- Andreas Abel <>< Du bist der geliebte Mensch. Department of Computer Science and Engineering Chalmers and Gothenburg University, Sweden andreas.abel(a)gu.se http://www.cse.chalmers.se/~abela/

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[ANN] bytestring-0.11.5.0 and bytestring-0.12.0.0
by Matthew Craven 07 Jul '23

07 Jul '23

On behalf of the maintainers team I'm happy to announce that two new bytestring versions have been released: * bytestring-0.11.5.0 is expected to be the last release in the bytestring-0.11 series. * bytestring-0.12.0.0 bundles all of the planned breaking changes that have been in the pipeline for the last few years. Highlights from the changelog (https://github.com/haskell/bytestring/blob/0.12.0.0/Changelog.md) * Some recently-discovered bugs in the SIMD implementations of isValidUtf8 have been fixed. * With bytestring-0.12.0.0, ShortByteString can now be safely coerced to or from the ByteArray type. * Many functions returning StrictByteString can now return their results unboxed. Many people contributed their time and effort to make this release happen. Thanks to all of them! Just to name a few, in no particular order: * Viktor Dukhovni * Vaibhav Sagar * Simon Jakobi * Matthew Craven * Andrew Lelechenko * Sergey Vinokurov * Koz Ross * Every contributor to past bytestring releases Happy Haskelling! ~-Matthew Craven

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Proposal: add laws to MonadError
by Alexandre Esteves 06 Jul '23

06 Jul '23

I ran into a scenario where the use of MonadError would only be valid if catchError (pure a) h = pure a was a law, so I looked up the laws in https://hackage.haskell.org/package/mtl-2.3/docs/Control-Monad-Error-Class.… but surprisingly found none. One would expect to see 1. catchError (pure a) h = pure a 2. catchError (throwError e) h = h e 3. throwError e >>= f = throwError e which would rule out silly instances like instance MonadError () Maybe where throwError () = Nothing catchError _ f = f () Searching for "monad error laws" gives me no haskell results, only https://typelevel.org/blog/2018/04/13/rethinking-monaderror.html which suggests the same laws. I propose adding these 3 laws to MonadError haddocks. AFAICT the IO/Maybe/Either/ExceptT instances in https://hackage.haskell.org/package/mtl-2.3/docs/src/Control.Monad.Error.Cl… all obey the laws.

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