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propensive's profile
Jon Pretty
Jon Pretty
Jon Pretty
@propensive

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Jon Pretty

@propensive

Supporting Scala through professional training and open-source software. Responsible for Magnolia, Fury, Scala World and Functional Africa.

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Joined July 2010

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    1. Jon Pretty‏ @propensive Jan 19

      The obvious benefit of extension methods is that they allow us to append methods to a type *after* it has been defined. But an undervalued advantage is that they append methods to *types*, with all the flexibility Scala gives us to specify those types precisely or generally.

      2 replies 1 retweet 17 likes
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    2. Alex Nedelcu‏ @alexelcu Jan 19
      Replying to @propensive

      You're right, except when it doesn't work. One common gotcha is that class methods have a higher priority than extension methods. And we can't specify priorities for extensions defined by 2 different parties.

      1 reply 0 retweets 3 likes
    3. Alex Nedelcu‏ @alexelcu Jan 19
      Replying to @alexelcu @propensive

      E.g. if you define an opaque type + flatMap is very different from a class + a flatMap method. The later can specify a flatMap method with a more flexible signature than Monad.flatMap, whereas the former cannot do it. Kind of pisses me off 🙂

      2 replies 0 retweets 1 like
    4. Alex Nedelcu‏ @alexelcu Jan 19
      Replying to @alexelcu @propensive

      This goes for OOP inheritance too. If you respect the method's contravariance for input, covariance for output, an overridden method can have a more specific signature than the method it overrides. There are non-obvious limits to extensions, which makes them "not a method".

      1 reply 0 retweets 1 like
      Jon Pretty‏ @propensive Jan 19
      Replying to @alexelcu

      I read this after my reply, but I think we're talking about the same thing. :)

      3:17 AM - 19 Jan 2021
      • 1 Like
      • Alex Nedelcu
      0 replies 0 retweets 1 like

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