RE: [Jscheme-user] Arbitrary precision integers

[<bor...@ko...>]

Hi Ken, Timothy

| Your definition is wrong=2E  Try this:
| (define fact=20
|     (let ((one (BigInteger=2E "1")))
|       (lambda (n)
|         (if (=3D 0 (=2EintValue n))=20
|             one
|             (=2Emultiply n (fact (=2Esubtract n one)))))))

I feel ridiculous=2E=2E=2E=2E, I typed this quickly just to check whether
BigInteger actually worked well before sending the email=2E
=20
| >And then I had to stop the evaluation of (fact (BigInteger "1000"))=20
| >after 20 minutes on a 1=2E6GHZ, 512MB laptop=2E Scheme=20
| implementations that=20
| >I've played with in the past would return the result almost=20
| right away=20
| >on much slower machines=2E
| >
| >Anyway, the concern is really practical, not just for the=20
| sake of it=2E=20
| >I'm getting integer overflows while trying to solve a very practical=20=

| >problem=2E
|=20
| Have you tried using longs?

No, I will=2E It may well work in my particular situation=2E=2E=2E=2EHowev=
er, in
InputPort=2EreadWholeNumber the U=2EtoNum(long) method is always invoked
regardless of how the number is written=2E And that method will yield an
Integer object whenever the constant is within the Java int range=2E Would=
n't
that matter in subsequent calculations? Again, I am only superficially
familiar with the code, I just starated using Jscheme=2E

| >If you have thought about this and have ideas about what to do, I am=20=

| >willing to help with coding, testing etc=2E
| >
| >BTW, I think Jscheme is great!
|=20
| Thanks!
|=20
| I've been thinking there should be an extension library that=20
| would let you do this=2E  Perhaps we can develop one=2E Here's a=20
| simple one that provides big integers and big rational=20
| numbers, i've been playing with=2E

I think this makes sense, but only as a workaround=2E When typing gets so
fine grained, and in a language without operator/function overloading, it
becomes quite difficult to make a program evolve, reuse libraries with
algorithms that one needs etc=2E I can't always know in advance whether I
need a big integer, a long or a 32 bit value, I can't use a library writte=
n
with longs for my "big integer problem"=2E The fact that if I want to work=

with, say, precisely 32-bit integers is really cool, but I shouldn't be
forced to make that decision when I am not getting anything out of it=2E

Perhaps there is a problem with the Java interfacing - those number type
distinctions seem important only for that purpose=2E But probably a sensib=
le
method resolution can be easily found=2E Also, wasn't there a type casting=

syntax in Jscheme for Java method invokation?=20

I would say that it makes sense to represent integers in Jscheme with a
BigInteger whenever a Java modifier is not used in a number constant=2E

Thanks for your responses!
Best,
Boris

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