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drij

Sun Oct 12, 2008 2:18 pm


Larger Integers

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I was working my way through the problems on Project Euler when I encountered an issue with fcn isPrime (maybePrime : int) : boolean
    var hasNoFactors : boolean := true

    if maybePrime = 1 or maybePrime = 2 then
        result true
    end if

    for maybeFactor : 2 .. floor (sqrt (maybePrime))
        if maybePrime mod maybeFactor = 0 then
            hasNoFactors := false
        end if
    end for

    result hasNoFactors
end isPrime
After I wrote this, I couldn't figure out how to deal with the size of the number 600851475143.

My question is, is it possible to work with large numbers such as this in turing?


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OneOffDriveByPoster

Sun Oct 12, 2008 4:52 pm


Re: Larger Integers

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Yes, the double-precision floating point can represent at least this, and all the integers >= 0 below it exactly.


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Saad

Sun Oct 12, 2008 4:58 pm


RE:Larger Integers

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But it should be known that it can not represent accurately be represented. Unfortunately Turing has no default way of handling them with full accuray. You could make your own though.


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Insectoid

Sun Oct 12, 2008 9:02 pm


RE:Larger Integers

-----------------------------------

does Turing not support 'long' variables?


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Saad

Sun Oct 12, 2008 9:46 pm


RE:Larger Integers

-----------------------------------

None to my knowledge


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[Gandalf]

Sun Oct 12, 2008 9:48 pm


RE:Larger Integers

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Nope, it doesn't.  float is as much precision as you can get.


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drij

Mon Oct 13, 2008 10:27 am


Re: Larger Integers

-----------------------------------

Ok then. Thanks for all your replies.  :)


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[Gandalf]

Mon Oct 13, 2008 7:20 pm


RE:Larger Integers

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If you're looking to get further ahead in Euler, and are willing to learn a new language that's not too difficult, I'd recommend Ruby or Python.  Both, AFAIK, support arbitrarily long integers by default.