Re: [boost] Re: Extended binary numbers

From: Dan Nuffer (dnuffer_at_[hidden])
Date: 2000-09-21 09:35:15

Beman Dawes wrote:
> 
> At 03:38 PM 9/20/2000 -0600, Dan Nuffer wrote:
> 
>  >A few years ago I wrote a class like this.  It acts like a signed
>  >integer and the range is only limited to the amount of memory you have.
>  >You can download it from:
>  >http://students.cs.byu.edu/~nuffer/bigint.h
>  >http://students.cs.byu.edu/~nuffer/bigint.cpp
>  >
>  >I placed it into the public domain, and anyone is free to use it.  If
>  >there is interest, it could be cleaned up and submitted to boost.  It
>  >also needs some performance work, as I took the straightforward, easy to
>  >code approach and didn't do any fancy algorithms.
> 
> Dan,
> 
> Did you look at Daryle Walker's
> http://www.egroups.com/files/boost/bitint.zip posting?
> 
> Did your classes have any advantages over Daryle's?
> 
> --Beman

Yes.  The number of bits in bitint is fixed at compile time.  My bigint
class dynamically allocates memory as needed.  Allowing the user to
store a number as large as you have memory.  There are situations where
bitint is a more appropriate solution, and others where bigint is
better.  For example, say you wanted to write a program to compute
factorials.  You don't know how big of a factorial the user wants to
compute until run-time, so my class would be the appropriate solution in
that case.  Given enough memory and time, one could compute the
factorial of 1,000,000,000,000.  Looking back, I think I created this
class to use when messing around with Ackermann's function, but it ended
up not being much help because Ackermann's function takes a LONG time to
compute for almost any values.  Anyway, there are a few things that need
cleaning up (operator <<) but all of the functionality of an integer is
present, debugged and free for anyone to use.

--Dan