-------------------------------------------------------------------------------- Fedora Update Notification FEDORA-2010-18820 2010-12-11 23:34:05 --------------------------------------------------------------------------------
Name : ghc-neither Product : Fedora 13 Version : 0.1.0 Release : 1.fc13 URL : http://hackage.haskell.org/package/neither Summary : Either with monad and applicative instances Description : The standard Either datatype suffers from a lack of monad and applicative instances. To make matters worse, the mtl and transformers packages provide orphan instances which conflict with each other, as well as defining a transformer version which has an usually unnecessary superclass constraint. Besides these annoyances, there is another issue: there exist two reasonable definitions of the Applicative instance for Either: one the holds onto only the first Left value, or one that appends all Left values together via a Monoid instance. The former is compatible with the monad instance, while the latter is not. This package defines three datatypes, some helpers functions and instances. The data types are AEither, MEither and MEitherT. AEither provides an Applicative instance which appends Left values, MEither provides the monadic definition, and MEitherT is a monad transformer. This package provides the shared library. -------------------------------------------------------------------------------- Update Information: A simple type class for success/failure computations. =============== The standard Either datatype suffers from a lack of monad and applicative instances. To make matters worse, the mtl and transformers packages provide orphan instances which conflict with each other, as well as defining a transformer version which has an usually unnecessary superclass constraint. Besides these annoyances, there is another issue: there exist two reasonable definitions of the Applicative instance for Either: one the holds onto only the first Left value, or one that appends all Left values together via a Monoid instance. The former is compatible with the monad instance, while the latter is not. This package defines three datatypes, some helpers functions and instances. The data types are AEither, MEither and MEitherT. AEither provides an Applicative instance which appends Left values, MEither provides the monadic definition, and MEitherT is a monad transformer. -------------------------------------------------------------------------------- References: [ 1 ] Bug #630283 - Review Request: ghc-neither - Either with monad and applicative instances https://bugzilla.redhat.com/show_bug.cgi?id=630283 [ 2 ] Bug #630223 - Review Request: ghc-failure - A simple type class for success/failure computations https://bugzilla.redhat.com/show_bug.cgi?id=630223 -------------------------------------------------------------------------------- This update can be installed with the "yum" update program. Use su -c 'yum update ghc-neither' at the command line. For more information, refer to "Managing Software with yum", available at http://docs.fedoraproject.org/yum/. All packages are signed with the Fedora Project GPG key. More details on the GPG keys used by the Fedora Project can be found at https://fedoraproject.org/keys -------------------------------------------------------------------------------- _______________________________________________ package-announce mailing list [email protected] https://admin.fedoraproject.org/mailman/listinfo/package-announce
