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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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propensive.com
Joined July 2010

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    1. This Tweet is unavailable.
    2. Jon Pretty‏ @propensive 17 May 2019
      Replying to @jdegoes

      I'm still not sure how easy it will be to remove one type from a union. That would be a gamechanger in error-handling ergonomics.

      0 replies 0 retweets 6 likes
    3. This Tweet is unavailable.
    4. Jon Pretty‏ @propensive 18 May 2019
      Replying to @jdegoes

      There's a reason for it, which is that set union and intersection (types are just sets of properties) don't have unique inverses. (A∪B)∪B = A∪B. What would the inverse of ∪B be? One could argue for A or A∪B, but only A∪B is ⊇ A ∀ A, B; hence, the only general solution.

      0 replies 0 retweets 5 likes
    5. This Tweet is unavailable.
    6. Lander‏ @LanderLo 18 May 2019
      Replying to @jdegoes @propensive

      Due to Scala's subtyping hierarchy, that proof is impossible as there's no true orthogonality. It would require establishing some kind of arbitrary LUB ceiling, e.g. Any*, Exception,... outside stdlib, etc.

      0 replies 0 retweets 0 likes
    7. This Tweet is unavailable.
    8. Lander‏ @LanderLo 18 May 2019
      Replying to @jdegoes @propensive

      Failing to see how A∩B=∅ is possible when there is no true orthogonality in the scala typesystem.Any two types will at least intersect on Any. E1 | E2, extend Exception in the wild, even when pure a custom Error supertype is common.Arbitrary exclusions required

      1 reply 0 retweets 0 likes
      Jon Pretty‏ @propensive 18 May 2019
      Replying to @LanderLo @jdegoes

      That's an intersection on *members*, not on *properties*. Duality!

      1:49 PM - 18 May 2019
      • 1 Like
      • Lander
      1 reply 0 retweets 1 like
        1. New conversation
        1. Lander‏ @LanderLo 18 May 2019
          Replying to @propensive @jdegoes

          Ah! I was thinking about the properties. The constructivist in me.

          1 reply 0 retweets 1 like
        2. Lander‏ @LanderLo 18 May 2019
          Replying to @LanderLo @propensive @jdegoes

          In fact the constructivist in me would reject the duality ;), There are only properties. What is this pretense that you can comprehend all the existing objects that meet those properties unless you close the world?

          0 replies 0 retweets 1 like
          3. End of conversation

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