diff options
| -rw-r--r-- | gnu/packages/haskell.scm | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/gnu/packages/haskell.scm b/gnu/packages/haskell.scm index 63d4360182..d3ff27412f 100644 --- a/gnu/packages/haskell.scm +++ b/gnu/packages/haskell.scm @@ -11608,6 +11608,60 @@ default) @end itemize") (license license:bsd-3))) +(define-public ghc-validation + (package + (name "ghc-validation") + (version "1.1") + (source + (origin + (method url-fetch) + (uri (string-append + "mirror://hackage/package/validation/validation-" + version + ".tar.gz")) + (sha256 + (base32 + "1acj7mh3581ks405xswxw6667z7y1y0slisg6jvp6chc191ji9l5")))) + (build-system haskell-build-system) + (arguments + `(#:phases + (modify-phases %standard-phases + (add-after 'unpack 'add-setup-script + (lambda _ + ;; The usual "Setup.hs" script is missing from the source. + (with-output-to-file "Setup.hs" + (lambda () + (format #t "import Distribution.Simple~%") + (format #t "main = defaultMain~%")))))))) + (inputs + `(("ghc-semigroups" ,ghc-semigroups) + ("ghc-semigroupoids" ,ghc-semigroupoids) + ("ghc-bifunctors" ,ghc-bifunctors) + ("ghc-lens" ,ghc-lens))) + (native-inputs + `(("ghc-hedgehog" ,ghc-hedgehog) + ("ghc-hunit" ,ghc-hunit))) + (home-page "https://github.com/qfpl/validation") + (synopsis + "Data-type like Either but with an accumulating Applicative") + (description + "A data-type like Either but with differing properties and type-class +instances. + +Library support is provided for this different representation, including +@code{lens}-related functions for converting between each and abstracting over +their similarities. + +The @code{Validation} data type is isomorphic to @code{Either}, but has an +instance of @code{Applicative} that accumulates on the error side. That is to +say, if two (or more) errors are encountered, they are appended using a +@{Semigroup} operation. + +As a consequence of this @code{Applicative} instance, there is no +corresponding @code{Bind} or @code{Monad} instance. @code{Validation} is an +example of, \"An applicative functor that is not a monad.\"") + (license license:bsd-3))) + (define-public ghc-concurrent-output (package (name "ghc-concurrent-output") |