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Small numbercial analysis question

  1. Aug 6, 2004 #1
    I was doing a small numbercal analysis problem that required the use of huge numbers. At first i was surprised that my code didn't work, even after double and triple checking, and after tracing the programme, i found out the mistake that i did. Firstly i used integers, and when the numbers started to increase they went bigger than the integer number range on C++ and started to give a negative number. Anyways, i used long and it worked ok for most of the numbers that needed calculations, but still some iteration couldn't be done since they also went out of range.

    How could i solve this problem?
  2. jcsd
  3. Aug 6, 2004 #2
    Wow, well in the case of integers it is a simpler problem. Extending floating point datatypes is more complicated.

    It is not so hard to create a larger integer class as long as you follow the same bitwise rules than intrinsic integer types follow. And the basic arithmetic operators can be overriden in C++ to make it pretty transparent.

    But to save you some trouble, there are many C++ numerics libraries out there that have already done this. Try starting with "c++ numerics library" in google.

    I can't speak for any of them because I haven't used them before.
  4. Aug 6, 2004 #3
    Thx, will do.

    Still open to more suggestions though :)
  5. Aug 6, 2004 #4
    Are 64 bits enough for you? If so then use long long (with g++) or __int64 (with VS); or their unsigned counterparts. Otherwise a quick solution might be to switch to Java and use the library class BigInteger.
  6. Aug 6, 2004 #5


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  7. Aug 6, 2004 #6
    Last edited: Aug 6, 2004
  8. Aug 10, 2004 #7
    I'm thankful. It hasn't occured to me to use Java, which i will be doing, and for educational purposed i'll also check out and test the links grady and robphy gave.
  9. Aug 11, 2004 #8
    If you don't have to work in Unix, get ubasic (free download) from

    It comes "ready to go" with built-in capability to handle integers and rational numbers up to 2600 DIGITS long, plus other impressive features.
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