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edwinbrady's profile
Edwin Brady
Edwin Brady
Edwin Brady
@edwinbrady

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Edwin Brady

@edwinbrady

CompSci Lecturer. Go player. Programming language researcher. Idris hacker. Denies knowledge of Whitespace. He/him. http://tinyurl.com/TypeDD 

St Andrews
eb.host.cs.st-andrews.ac.uk
Joined November 2008

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    1. rntz‏ @arntzenius 21 Apr 2018
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      rntz Retweeted Hillel

      I think this is a fair challenge. I verified left-pad in Agda; it isn't very pretty: https://gist.github.com/rntz/aaaaf7a0bdb1cc65c49adb6adde29728 … Admittedly, I don't think Agda is aimed at this kind of problem. Anyone who's up to date on verification for FP languages want to take a shot at it?https://twitter.com/Hillelogram/status/987432178840756225 …

      rntz added,

      Hillel @hillelogram
      Lots of people say "FP is easier to analyze than imperative code because of purity" but whenever I ask for evidence people look at me like I'm crazy. So I'd like to make a challenge: I'll provide three imperative functions, and your job is to convert them into pure functions.
      Show this thread
      2 replies 4 retweets 9 likes
    2. Hillel‏ @hillelogram 21 Apr 2018
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      Replying to @arntzenius

      Hillel Retweeted Ranjit Jhala

      Yeah, we got a few! @stevecheckoway did it in pure Dafny (https://rise4fun.com/Dafny/RF6L ), @RanjitJhala did it in LiquidHaskell (https://twitter.com/RanjitJhala/status/987728366189985792 …), and apparently @edwinbrady wrote a version for Idris that's part of the stdlib.

      Hillel added,

      Ranjit Jhala @RanjitJhala
      Replying to @hillelogram @GabrielG439
      Here's what a "full" proof of padLeft looks like with LH https://github.com/ucsd-progsys/liquidhaskell/blob/fix-clg/tests/pos/padLeft.hs … -- the code is Gabriel's but we prove the facts about sequences that Dafny bakes in as axioms...
      3 replies 0 retweets 4 likes
      Edwin Brady‏ @edwinbrady 21 Apr 2018
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      Replying to @hillelogram @arntzenius and

      Oh, did I? I was thinking it would be possible to set things up to do this neatly, but honestly I think your basic position is reasonable...

      2:38 PM - 21 Apr 2018
      • 3 Likes
      • vaibhav sagar ⏐ Τhе Αnⅽⅰеnt Вооеr ⏐ Hillel
      2 replies 0 retweets 3 likes
        1. New conversation
        2. Edwin Brady‏ @edwinbrady 21 Apr 2018
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          Replying to @edwinbrady @hillelogram and

          ...in that I find FP helps me understand a program, but only informally from what the types tell me. And the types help me be productive, but aren't necessarily for guaranteeing correctness beyond some small (but useful) properties.

          1 reply 1 retweet 5 likes
        3. Hillel‏ @hillelogram 21 Apr 2018
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          Replying to @edwinbrady @arntzenius and

          I know there's a lot of excitement about using DP for full proofs, but the main exciting thing for me is being able to push _some_ property tests onto the type system, like matrix multiplication or state machines

          1 reply 0 retweets 2 likes
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        2. Hillel‏ @hillelogram 21 Apr 2018
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          Replying to @edwinbrady @arntzenius and

          One of the fascinating things about this challenge is that none of big "FP > IP" advocates wrote successful proofs, while AFAICT all of the people who wrote successful proofs hold similar positions to mine: maybe prefer one in general, but which is "better" is contextual.

          2 replies 0 retweets 3 likes
        3. Hillel‏ @hillelogram 21 Apr 2018
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          Replying to @hillelogram @edwinbrady and

          Like I generally find it easier to think in state machines and contracts, but there's still plenty of problems where I'd find it much easier to think in function composition. I try to be excited about everything.

          1 reply 0 retweets 1 like
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