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expressive power and conceptual beauty is Lisp's core strength, not code maintainability or runtime performance. Well, Arc is actually very maintainable, and q

expressive power and conceptual beauty is Lisp's core strength, not code maintainability or runtime performance. Well, Arc is actually very maintainable, and quite fast. After all, HN is powered by Arc, and it serves >100k daily uniques on a single core.

peterhunt 13y ago
Yep! Not saying that it's impossible, just that some of the concepts that Lisp is based on make these things harder to pull off. The reason for this is that Lisp emphasizes flexibility, and the more flexible your runtime environment is, the more ways to do something, which makes it easier to have hard-to-maintain code (and harder to reason about performance, too). But it's not impossible to do with Lisp for sure.
- chongli 13y ago
  Lisp macros also provide ways to take ugly, hand-optimized code and clean it up to provide a cleaner, friendlier interface. Like all macros, this comes at no runtime cost (since all macros have been fully expanded by this point).
- sillysaurus 13y ago
  Actually, it's not any harder to write maintainable code in Arc. In many ways, it's much easier, because you write your program as a set of parts which fit together like an arch.
gohrt 13y ago
HN is fast because it is feature-barren. That's a design choice pg is free to make (and cutting features is a great way to improve performance), but not a proof of Arc/Lisp's ability to support complex applications with high-performance.
- sillysaurus 13y ago
  Which features would convince you that Arc is fast?
  - waterhouse 13y ago
    Just for the record, let's count to 100 million. And add the numbers up while we're at it. ~ $ time (echo '(do (= n 0) (for i 1 100000000 (++ n i)) prn.n (quit))' | arc) Welcome to Racket v5.3.5.1. Use (quit) to quit, (tl) to return here after an interrupt. arc> 5000000050000000 real 0m28.561s user 0m28.308s sys 0m0.249s ---- ~ $ time (echo -e 'n=0 \ni=0 \nwhile (i <= 100000000): \n n += i \n i += 1 \n\nprint(n)\n' | python3.3) 5000000050000000 real 0m30.244s user 0m30.230s sys 0m0.013s It would appear to be competitive with Python on my machine on this particular task. (Also you can make it faster by dropping into Racket.)
    - dzderic 13y ago
      A while loop and temporary mutable variables are definitely not the Pythonic way of doing this. More idiomatic: $ time python -c 'print sum(xrange(100000000 + 1))' 5000000050000000 real 0m1.398s user 0m1.383s sys 0m0.012s Comparison to baseline: $ time (echo -e 'n=0 \ni=0 \nwhile (i <= 100000000): \n n += i \n i += 1 \n\nprint(n)\n' | python) 5000000050000000 real 0m33.140s user 0m32.939s sys 0m0.023s
      - waterhouse 13y ago
        I see. That is good to know; I merely chose mutating global variables in a loop because I knew how to do that in both languages. (I am not very familiar with Python.) That is not the idiomatic way to do it in Arc, either. I would normally use a recursive function, like this: arc> (time:xloop (i 0 n 0) (if (> i 100000000) n (next (+ i 1) (+ n i)))) time: 9121 cpu: 9130 gc: 0 mem: 480 ; the times are in msec 5000000050000000 Or perhaps a "higher-order function": arc> (time:sum idfn 1 100000000) time: 19889 cpu: 19908 gc: 0 mem: 1224 5000000050000000 Or use a deforestation macro that I wrote, which is closest to your Python example: arc> (time:thunkify:reduce + (range 1 100000000)) time: 17971 cpu: 17985 gc: 0 mem: 3592 5000000050000000 Also, here's what you can get by dropping into Racket: arc> (time:$:let loop ((i 0) (n 0)) (if (> i 100000000) n (loop (+ i 1) (+ n i)))) time: 402 cpu: 403 gc: 0 mem: 920 5000000050000000 I suppose Python has an analogue of that--dropping into C, or at least loading C libraries. Which Racket can do too. Mmm.

peterhunt 13y ago

Yep! Not saying that it's impossible, just that some of the concepts that Lisp is based on make these things harder to pull off. The reason for this is that Lisp emphasizes flexibility, and the more flexible your runtime environment is, the more ways to do something, which makes it easier to have hard-to-maintain code (and harder to reason about performance, too). But it's not impossible to do with Lisp for sure.

chongli 13y ago
Lisp macros also provide ways to take ugly, hand-optimized code and clean it up to provide a cleaner, friendlier interface. Like all macros, this comes at no runtime cost (since all macros have been fully expanded by this point).
sillysaurus 13y ago
Actually, it's not any harder to write maintainable code in Arc. In many ways, it's much easier, because you write your program as a set of parts which fit together like an arch.

gohrt 13y ago

HN is fast because it is feature-barren. That's a design choice pg is free to make (and cutting features is a great way to improve performance), but not a proof of Arc/Lisp's ability to support complex applications with high-performance.

sillysaurus 13y ago
Which features would convince you that Arc is fast?
- waterhouse 13y ago
  Just for the record, let's count to 100 million. And add the numbers up while we're at it. ~ $ time (echo '(do (= n 0) (for i 1 100000000 (++ n i)) prn.n (quit))' | arc) Welcome to Racket v5.3.5.1. Use (quit) to quit, (tl) to return here after an interrupt. arc> 5000000050000000 real 0m28.561s user 0m28.308s sys 0m0.249s ---- ~ $ time (echo -e 'n=0 \ni=0 \nwhile (i <= 100000000): \n n += i \n i += 1 \n\nprint(n)\n' | python3.3) 5000000050000000 real 0m30.244s user 0m30.230s sys 0m0.013s It would appear to be competitive with Python on my machine on this particular task. (Also you can make it faster by dropping into Racket.)
  - dzderic 13y ago
    A while loop and temporary mutable variables are definitely not the Pythonic way of doing this. More idiomatic: $ time python -c 'print sum(xrange(100000000 + 1))' 5000000050000000 real 0m1.398s user 0m1.383s sys 0m0.012s Comparison to baseline: $ time (echo -e 'n=0 \ni=0 \nwhile (i <= 100000000): \n n += i \n i += 1 \n\nprint(n)\n' | python) 5000000050000000 real 0m33.140s user 0m32.939s sys 0m0.023s
    - waterhouse 13y ago
      I see. That is good to know; I merely chose mutating global variables in a loop because I knew how to do that in both languages. (I am not very familiar with Python.) That is not the idiomatic way to do it in Arc, either. I would normally use a recursive function, like this: arc> (time:xloop (i 0 n 0) (if (> i 100000000) n (next (+ i 1) (+ n i)))) time: 9121 cpu: 9130 gc: 0 mem: 480 ; the times are in msec 5000000050000000 Or perhaps a "higher-order function": arc> (time:sum idfn 1 100000000) time: 19889 cpu: 19908 gc: 0 mem: 1224 5000000050000000 Or use a deforestation macro that I wrote, which is closest to your Python example: arc> (time:thunkify:reduce + (range 1 100000000)) time: 17971 cpu: 17985 gc: 0 mem: 3592 5000000050000000 Also, here's what you can get by dropping into Racket: arc> (time:$:let loop ((i 0) (n 0)) (if (> i 100000000) n (loop (+ i 1) (+ n i)))) time: 402 cpu: 403 gc: 0 mem: 920 5000000050000000 I suppose Python has an analogue of that--dropping into C, or at least loading C libraries. Which Racket can do too. Mmm.