[boost] Interest in an arbitrary precision library?

From: Joel Eidsath (jeidsath_at_[hidden])
Date: 2005-09-02 13:23:23

I've used several different arbitrary precision libraries with C++ and I 
have always been somewhat disappointed.  And now I'm finally 
disappointed enough to start on my own. 

Here are the attributes that I think a C++ arbitrary precision library 
needs:

0)  As much as possible, the library types should be drop-in 
replacements for the built-in types.
       a)  This probably means some sort of numeic_limits support.  I am 
unclear on the best implementation of this.
       b)  Any automatic type conversions should  behave in an obvious 
manner.
       c)  Ease of use may take priority over efficiency.
1)  The library should be both useful for number theory and a way of 
improving code robustness by minimizing overflow errors.
2)  It should also provide equivalents of the basic C++ math functions.  
Implementing TR1 functions should be a priority.
3)  As well as arbitrary precision, it should provide error range math:  
2.00 * 2.00 is not generally the same thing as 2.0 * 2.0
4)  It should use fast algorithms for multiplication and division, but 
instead of trying to compete with other libraries in computation speed 
(GMP uses hand-coded assembly in places), it should concentrate on code 
portability and ease of extension.
5)  I do not envision any fancy memory management.  The "big int" class 
will probably use a std::vector<int> to store it's implementation data.
6)  Providing math functions beyond those already in C++ will not be a 
priority. 
        a)  GCD will be at least one exception to this. 
7)  It should work well with other Boost libraries where possible.
8)  Divide by zero errors for integers should be handled with an exception.
9)  Precision for rational numbers may be set as a static member 
variable or it may not.  In the second case, expressions involving 
rational numbers of different.
10)  Drop-in algorithm replacement for various operations might be a 
nice feature.

Comments, suggestions, desired features?  Some of the parts of this list 
are off the top of my head, so feel free to suggest changes.

Joel Eidsath