Huge Numbers in C++

This is a discussion on Huge Numbers in C++ within the C++ Programming forums, part of the General Programming Boards category; Hi guys... I'm pretty new to C++. I'm working with Visual C++ 6.0 on Windows XP, doing mainly console apps ...

  1. #1
    jdm
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    Huge Numbers in C++

    Hi guys...
    I'm pretty new to C++. I'm working with Visual C++ 6.0 on Windows XP, doing mainly console apps at the moment.

    My question deals with how C++ handles large numbers--like > 5,000,000,000. As I understand it, the biggest number that an int variable can handle is 2,147,483,647, and the biggest than an unsigned int can handle is 4,294,967,295. That ok for most programs... but I can't imagine that no C++ application is able to handle bigger numbers!

    Any solutions are welcome--either accepted methods or rough hacks. Is there maybe a header file that I can include that will give me additional data types? Like I said I'm pretty new to this (although I'm familiar with many web-based languages, like JavaScript, PHP, and ASP, so I know the principles of OOP programming). Any help you can provide is extremely welcome... but please treat me like the dumbest programmer you've ever met! All the details are important to me. Thanks!

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    jdm
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    By the way, here's the program I'm working on. The goal is to figure out the probabity of 2 out of 100 people in a room sharing the same birthday. Right now, I'm trying to find the probability of the two people not sharing the same day, and the program is coded to generate the numerator:

    Code:
    #include <iostream>
    using namespace std;
    
    int main(void)
    {
    	int numDays = 365;
    	int numPeople = 100;
    	unsigned int product = 1;
    	for (int i = 0; i < numPeople; i++)
    	{
    		product = product * (numDays - i);
    		cout << product << "\n";
    	}
    
    	return 0;
    }
    Thanks again!

  3. #3
    Registered User Codeplug's Avatar
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    Here are some threads you can read:
    http://cboard.cprogramming.com/search.php?searchid=5250

  4. #4
    & the hat of GPL slaying Thantos's Avatar
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    Code:
    #include <iostream>
    
    int main(void)
    {
      unsigned long long int x= (unsigned long long)-1;
      cout<<"Size:  "<< sizeof x<<endl;
      cout<<"Value: "<< x <<endl;
      return 0;
    }
    Output:
    Size: 8
    Value: 18446744073709551615

  5. #5
    Registered User major_small's Avatar
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    Quote Originally Posted by Codeplug
    nice link...

    look around for a program called 'BigInt' or something to that effect... I've seen it around as a case study-type thing for school courses... I'm not sure if it'll do exactly what you want though...
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  6. #6
    C++ Witch laserlight's Avatar
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    There's the GNU MP library
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  7. #7
    Registered User Codeplug's Avatar
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    Damn, I just realized my link is no longer valid....

    It was a search on "GMP".

    gg

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    Thantos your code gave me an error about long followed by long is illegal. I found that this though would give the same ouput:
    Code:
    #include <iostream>
    
    int main()
    {
    	unsigned __int64 x = (unsigned __int64)-1;
    	std::cout << x << std::endl;
    }

  9. #9
    Registered User Codeplug's Avatar
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    __int64 is MSVC specific....

    change "unsigned long long int" to "unsigned long long"

    gg

  10. #10
    & the hat of GPL slaying Thantos's Avatar
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    Try the following:

    cout<<sizeof (long);

    If it is 8 then use unsigned long instead of long long.

  11. #11
    Registered User Codeplug's Avatar
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    Quote Originally Posted by Codeplug
    change "unsigned long long int" to "unsigned long long"
    My bad....

    "long long int" is C99 and is suppored in C89 mode by GCC as a compiler extension.

    Here's the scoop:
    http://gcc.gnu.org/onlinedocs/gcc/Long-Long.html

    gg

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    Well normally you would use a 'long' variable for these types of things, as those types of variables reserve more memory, they can take a greater value. And then theres math where you can seperate variables and treat them like normal numbers in base 10. For instance if you had a huge number..lets say 500000000000000000..just some huge number. If you seperated that into multiple variables and _dealt_ with them as one in your programs math/calculations, then you have a way of actually accomplishing that feet.
    OS: Windows XP Pro CE
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    i also need to use big numbers in an encryption program i am working on.
    but i need numbers about 1 * 10^1000
    how do i get numbers so big?
    i downloaded that gmp, but i get lots of errors

  14. #14
    mustang benny bennyandthejets's Avatar
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    how do i get numbers so big?
    I would write a class to replace all the C++ primitives. By overloading all the required operators, it can function like a standard primitive. It would store your large numbers by splitting it up into sections that can be described by scientific notation, and then added to each other. Or something like that.
    benforbes@optusnet.com.au
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