Re: Proposal: add `on` to the Prelude

Bleh. Now we have two functions that do the same thing, both in base... I don't want "on" in prelude but this seems far worse to me than the original proposal. Let's stick with that one for now and if it dies you can propose this separately? :D On Thu, Sep 12, 2019 at 11:15 AM David Feuer wrote:

No, there's certainly no need to remove the existing function.

On Thu, Sep 12, 2019, 10:57 AM Elliot Cameron wrote:

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You might be on2 something.

But then you rename it in Data.Function too and break backward compat??

On Thu, Sep 12, 2019 at 10:55 AM David Feuer wrote:

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For whatever it's worth, the unidiomatic but arguably more logical name `on2` has no hits on Hoogle.

On Tue, Sep 10, 2019, 6:59 PM David Feuer wrote:

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Indeed, there are a lot more conflicts than I'd have expected. Ignoring functions with the same type, Hoogle shows this name in the below packages. I have no sense of the overall significance of the specific packages or (equally importantly) of the `on` function within each.

haskell-gi-base: on :: forall object info m . (GObject object, MonadIO m, SignalInfo info) => object -> SignalProxy object info -> HaskellCallbackType info -> m SignalHandlerId

brick: on :: Color -> Color -> Attr

esqueletto: on :: SqlExpr (Value Bool) -> SqlQuery ()

relational-query (both): on :: MonadQuery m => Predicate Flat -> m () on :: MonadQuery m => QueryA m (Predicate Flat) ()

threepenny-gui: on :: (element -> Event a) -> element -> (a -> UI void) -> UI ()

miso: on :: MisoString -> Decoder r -> (r -> action) -> Attribute action

wild-bind: on :: i -> v -> Binder i v ()

massiv-io: on :: Pixel X Bit

selda-postgresql: on :: Text -> Text -> PGConnectInfo

On Tue, Sep 10, 2019, 6:42 PM Ryan Trinkle wrote:

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One note: this does conflict with some other libraries, for instance GTK2HS

On Tue, Sep 10, 2019 at 6:26 PM chessai . wrote:

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+1

On Tue, Sep 10, 2019, 5:53 PM David Feuer wrote:

> Every time I reach for Data.Function.on, I feel like a total dolt > for having to import a module to get a function whose implementation is > barely longer than the import. And it's a really good function too! Can we > please add it to the Prelude? > > on :: (b -> b -> c) -> (a -> b) -> a -> a -> c > (.*.) `on` f = \x y -> f x .*. f y > _______________________________________________ > Libraries mailing list > Libraries@haskell.org > http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries > _______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries

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