Proposal: add `on` to the Prelude

Ryan Trinkle ryan.trinkle at gmail.com
Tue Sep 10 22:42:31 UTC 2019


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

On Tue, Sep 10, 2019 at 6:26 PM chessai . <chessai1996 at gmail.com> wrote:

> +1
>
> On Tue, Sep 10, 2019, 5:53 PM David Feuer <david.feuer at gmail.com> 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
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