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3 points by rocketnia 3225 days ago | link | parent

Your examples can be simplified quite a bit. ^_^

  ; Move a chain of n cards from i to j.
  (zap [let (taken leftovers) (split _.i n)
         (copy _ i leftovers j (join taken _.j))]
       the-piles)
  
  
  ; Reveal the top card of the nth pile.
  
  (def copdate (orig . kvs)
    (apply copy orig (mappend [list _.0 (_.1:orig _.0)] pair.kvs)))
  
  (zap [copdate _ n [cons (list _.0 t) cdr._]] the-piles)
In principle I agree, disabling the programmer's ability to use mutation without reason is just frustrating. But I don't expect an example to help show this; most examples we could come up with would probably have easy-in-hindsight solutions like this. I think the point is that mutation gives us more easy ways to do things, so that we can quickly experiment and stuff.


2 points by akkartik 3222 days ago | link

  ; Reveal the top card of the nth pile.
  
  (def copdate (orig . kvs)
    (apply copy orig (mappend [list _.0 (_.1:orig _.0)] pair.kvs)))
  
  (zap [copdate _ n [cons (list _.0 t) cdr._]] the-piles)
How the heck is this 'simplified' compared to:

  (set:cadar the-piles.n)
? :)

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1 point by rocketnia 3222 days ago | link

I see you want to push the example to its limit a bit. ^_^ Well, I assume this hypothetical language would be stocked with utilities that made up for what its pureness missed out on. How believable are these?

  (def zipdate (func subject . indices)
    (iflet (first . rest) indices
      (copdate subject first [apply zipdate func _ rest])
      func.subject))
  
  (def zet (subject . args)
    (apply zipdate [do t] subject args))
  
  (zap zet the-piles n 0 1)

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1 point by evanrmurphy 3221 days ago | link

Was he calling it a simplification of one of waterhouse's more complex snippets, such as the one below?

   (= the-piles
       (join (take (- n 1) the-piles)
             (list:cons (list (car the-piles.n) t) (cdr the-piles.n))
             (drop n the-piles)))

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1 point by rocketnia 3221 days ago | link

That's definitely what I meant, and I was going to just say so, but whan I saw the ":)" I realized akkartik probably knew that and meant something like "that may not be 'oh god' complicated, but it's still not nearly as convenient as the mutating code." I don't know if that's a correct interpretation, but it made it more interesting to respond. ^_^

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1 point by akkartik 3221 days ago | link

No I didn't think about it nearly that much, just misunderstood which snippet you were responding to :/

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1 point by rocketnia 3221 days ago | link

Oh, then I'm glad that's resolved now. XD;;

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