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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. Jon Pretty‏ @propensive 16 Jul 2020

      100 brown-eyed and 100 blue-eyed perfect logicians live on an island, but none knows the color of their own eyes. There are no mirrors on the island, and communicating is forbidden. If any of them works out the color of their eyes, they must leave the island in the night.

      8 replies 12 retweets 40 likes
      Show this thread
    2. Jon Pretty‏ @propensive 16 Jul 2020

      One day a visitor comes to the island and says, "I see at least one person with blue eyes". What happens next? The surprising result is that nothing happens for a hundred days, then all the blue-eyed people leave, and the next night all the brown-eyed people leave.

      7 replies 0 retweets 2 likes
      Show this thread
      Jon Pretty‏ @propensive 16 Jul 2020

      This is a fun example of a riddle with a counter-intuitive solution, which can be demonstrated inductively. But like many similar riddles, different people will approach it in different ways.

      3:50 AM - 16 Jul 2020
      • 2 Likes
      • Daniel Coldham justinhj
      1 reply 0 retweets 2 likes
        1. New conversation
        2. Jon Pretty‏ @propensive 16 Jul 2020

          What's interesting to me about it is that programmers and mathematicians will typically accept the (contrived) scenario unquestioningly, and get to work solving it as the riddler intended, whereas other people will spend a long time questioning details intended to be irrelevant.

          2 replies 1 retweet 11 likes
          Show this thread
        3. Jon Pretty‏ @propensive 16 Jul 2020

          Could someone see a reflection of their eyes in some water? Could some of them work out their eye color from genetics? Why do they have to leave in the night, and what if they don't? What if one of them makes a mistake? These questions all miss the intent.

          1 reply 0 retweets 6 likes
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        4. Jon Pretty‏ @propensive 16 Jul 2020

          The mathematically-minded have learned, through practical experience, to ignore those details. This is certainly a skill, and a useful one for anyone writing code for a living.

          2 replies 0 retweets 9 likes
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        5. Jon Pretty‏ @propensive 16 Jul 2020

          But the same people can have a tendency to apply these abstraction skills to real-life scenarios, as if they were contrived by a puzzle-setter; with great swathes of detail disregarded as irrelevant, and moral equivalence established between ostensibly quite different situations.

          1 reply 1 retweet 18 likes
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        6. Jon Pretty‏ @propensive 16 Jul 2020

          I think it's unfortunate that something that is a useful skill for reasoning in some contexts may be so detrimental to reasoning in some other contexts, and as a programmer, I sometimes wish that my own zeal to snap to some perceived essence of a problem wasn't so strong.

          3 replies 2 retweets 33 likes
          Show this thread
        7. End of conversation

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