• Victor
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    17 months ago

    Out of curiosity, what kind of data do you generate with Haskell? And would be willing to show an example of a one or two liner that generates the data? 🙏

    • @[email protected]
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      7 months ago

      Uh, let’s look at my GHCi history…

      It looks like I was last searching for 12-member sets of permutations of 7 which come close to generating every possible permutation of seven elements, as well as meeting a few other criteria, for an electronics project. It ended up being more like 10 lines plus comments, though, plus a big table generated by GAP, which I formatted into a Haskell list using probably a line of Haskell plus file loading.

      Unfortunately for providing code, me playing with the finished algorithm has eaten up my whole 100 lines of history. So, here’s a two-liner I posted on Lemmy before, that implements a feed-forward neural net. It’s not exactly what you asked for, but it gives you an idea.

      layer layerInput layerWeights = map relu $ map sum $ map (zipWith (*) layerInput) layerWeights
      
      foldl layer modelInput modelWeights
      

      In practice, you might also need to define relu in another line:

      relu x = if x > 0 then x else 0

      Edit: No wait, I think that was a different problem related to the same project. There’s another module attached that generates all permutations of n items. After breaking it up so it’s a bit less write-only:

      allPermutations :: Int -> [[Int]]
      allPermutations 1 = [[0]]
      allPermutations n = concat $ map (addItem $ allPermutations (n-1) ) [0..(n-1)]
      
      addItem :: [[Int]]  -> Int -> [[Int]]
      addItem old new = map (\y -> new : map (fitAround new) y) old
      
      fitAround :: Int -> Int -> Int
      fitAround n y
      	| y >= n	= y+1
      	| otherwise	= y
      
      • Victor
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        17 months ago

        Cool! Thank you for sharing!

        I just recently read the man page for GNU Parallel, and that seems like a pretty nifty tool to generate permutations of data as well. It’s command-line so great for scripts, utilizes many cores, quick to do without mind-bending Haskell project setup, etc…, for anyone interested. 🙂👍

        • @[email protected]
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          17 months ago

          I’ll look into it, although this probably wasn’t directed at me. GHC can compile multi-threaded, and “setup” here was just opening GHCi and starting, and then moving it into files once it got large enough I didn’t want to repeat the work, so I’m happy.

          • Victor
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            27 months ago

            I still haven’t been able to learn project setup with Haskell and know exactly what I’m doing lol. But I’m glad you have a working setup! But yeah, do look into parallel if you want, maybe it can prove useful, or not. It was directed at you, considering your use case of generating permutations. :-)

            Take care!

      • Victor
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        7 months ago

        BTW: I think you need to put the “```” on separate lines.

        test

        test
        

        Edit: huh, nope, that had no difference in effect for me. Wonder why your code doesn’t render for me…

        • @[email protected]
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          17 months ago

          Which frontend are you on? I’m using lemmy-ui (the default webapp) and it renders fine, not sure how to find which version.

          • Victor
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            17 months ago

            I was using Sync for Lemmy when your comment didn’t render properly. No idea why. Especially since my own comments were rendering fine. 🤷‍♂️

            • @[email protected]
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              27 months ago

              I’d guess it has to do with the specific symbols I was using, and there’s a bug in rendering of markdown in Sync.