Re: Large numbers (or is Ada the choice for me?)

[dvdeug@x8b4e53cd.dhcp.okstate.edu (David Starner)]

On Fri, 9 Mar 2001 14:35:42 -0500, Marin David Condic <marin.condic.auntie.spam@pacemicro.com> wrote:
>"Hans Georg Schaathun" <georg@ii.uib.no> wrote in message
>news:slrn9ai9uk.iv9.georg@apal.ii.uib.no...
>> I need a tool to solve large systems of linear equations, with no
>> floating point operations (or any other approximations) allowed.
>> Even though I am not a seasoned programmer, I think I'll have to
>> write the tool myself.
>>
>This is a hopeless mission. Consider the instant you're row reduction
>results in 1/3 - can you put that into a computer *without* an approximation
>and still do math on it? The only issue then is how much accuracy is enough?

Yes. Computers can handle fractions just fine with the appropriate 
package. I'm not sure it's feasible to have no approximations in a large
system of linear equations, but it's possible.

>A good place to start looking for Ada software is: http://www.adapower.org/
>A quick Google search with the words "Ada Linear Algebra" yielded:
>http://www.cc.utah.edu/~nahaj/ada/math/linear.ads.html
>http://www.masstech.com/mpdesc.htm
>
>See also:
>http://lglwww.epfl.ch/Team/MW/mw_components.html
>
>As I recall Mats Weber had some Linear Algebra stuff in Ada...

He also has a big number package. If efficency is key, I might look
at the binding to gmp (http://www.ii.uib.no/~gisle/adagmp/).

>easier than in most languages because you can create a package to house the
>whole thing and use it just as if it was a native data type. 

Not easier than any other language with operator overloading and packages.
(C++ would be significantly easier, as Ada won't let you make a type
that "looks like" an integer.)

>Nope. Nope and Not Applicable. You're either going to have to download
>someone's large-number-package(s) or roll your own. I know of no general
>purpose languages that are going to give you math on that big a scale right
>out of the box. 

Common Lisp would give you the rationals and the big numbers out of
the box. 

-- 
David Starner - dstarner98@aasaa.ofe.org
Pointless website: http://dvdeug.dhis.org
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