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I had to write the following to understand this is going to converge to 6: >> 1/((1..1000000).map{|n| (1/((n*3.14)**2))}.inject{|a,b| a+b}) => 5.993921

• RiderOfGiraffes 17y ago
  >>> from math import pi >>> 1/sum( [1/(pi*n)**2 for n in xrange(1,1000)] ) 6.00365160802217
  • apgwoz 17y ago
    let's not get all fizzbuzz-y in here...
  • antirez 17y ago
    Shorter but, "ad hoc" like everything in Python (the reason I never liked it). The Ruby version looks like math, if you know the concepts of map and reduce it's trivial to understand what's going on. Compare this with sum() + "for n" and "xrange". Also if I remember some Python correctly "xrange" is almost like "range" but it's something like a lazy version, another ad-hoc stuff. Sorry, didn't resisted.
    • RiderOfGiraffes 17y ago
      Each to his/her own. This isn't intended to be a language war. If you prefer map and reduce then you can have them: >>> from math import pi >>> add = float.__add__ >>> def f(x): return (pi*x)**(-2) >>> 1/reduce(add, map(f,range(1,1000)) ) 6.0036796863530508 Or, as a one-liner: >>> 1/reduce(float.__add__, map(lambda x:1.0/(3.1416*x)**2,range(1,1000)) ) People who aren't mathmos often find the list comprehensions more comprehensible, hence the version I wrote not as a competitor, but as an alternative, to yours. Horses for courses. Personally, I've found the Python version to look more like math when I choose to express it like math, but I'm programming, so why not make it look like what I'm doing? Golf is a stupid game in programming. Understandability is the goal, but different readers find different things natural. That's never going to go away.
      • antirez 17y ago
        I guess it's really a matter of tastes indeed. My point is that, no matter the fact that I can try to mimic the Python idiomatic way or the reverse, there is a real difference between this languages, and is a difference that I see in many other languages, splitting them into two families: the "tools" languages that try to provide already build abstractions able to solve common problems, and the "concepts" languages where there are just a few rules you can combine to solve problems. I love the latter approach.
  • jrockway 17y ago
    Prelude> 1/sum ([1..1000] >>= \x -> [(pi*x)**(-2)]) 6.003647956020607
• andrewparker 17y ago
  Sorry if this is obvious, dusting off the math mind here... How is this solved without brute force computation?
  • RiderOfGiraffes 17y ago
    It's neither obvious nor easy. It was an outstanding problem in the mid 1700's, and it was Euler that solved it but some superbly reckless arguments. Euler's original paper: http://www.17centurymaths.com/contents/euler/e041tr.pdf http://www.17centurymaths.com/contents/euler/e041tr.pdf The bottom of this page has a more modern treatment, although it takes a lot for granted: http://www.math.wpi.edu/IQP/BVCalcHist/calc3.html http://www.math.wpi.edu/IQP/BVCalcHist/calc3.html Another treatment of Euler's proof is here: http://library.thinkquest.org/28049/Summing%20reciprocals.html http://library.thinkquest.org/28049/Summing%20reciprocals.ht...
    • stilist 17y ago
      Last link needs to swap %20 for the space.
      • RiderOfGiraffes 17y ago
        Done - thanks.