Wed, 22 Sep 1993 07:27:21 GMT

Related articles |
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Multiprecision Integer Math Package bert@netcom.com (1993-09-22) |

Re: Multiprecision Integer Math Package daveg@thymus.synaptics.com (Dave Gillespie) (1993-09-22) |

Re: Multiprecision Integer Math Package bothner@cygnus.com (1993-09-26) |

Newsgroups: | sci.math,comp.lang.c,comp.lang.c++,comp.sources.d,comp.compilers,comp.dsp |

From: | bert@netcom.com (Roberto Sierra) |

Followup-To: | sci.math,comp.lang.c,comp.lang.c++ |

Keywords: | C, arithmetic |

Organization: | Tempered MicroDesigns |

Date: | Wed, 22 Sep 1993 07:27:21 GMT |

Hello all --

I just wanted to let y'all know that there is an interesting thread

developing on sci.math which some of you may want to check out and

contribute to. Check out the 'Re: Multiprecision C sources?' thread

to come up do date on what's been discussed so far.

QUICK SUMMARY

There's a fellow who will soon be releasing a free C++ library to

perform extended precision integer arithmetic. It would allow

phenomenally large integers to be operated on using standard C-like

syntax by overloading all of the arithmetic operators. Here's just

a teeny example (the integers could be *much* larger):

bsint a = "384398349854857384759834758734958374519";

bsint b = "31415925634982429872345023042034982374";

bsint c;

c = a + a/b;

[Full precision result ends up in c.]

This obviously has applications in math, possibly physics and other

sciences where a large number of events might need to be counted,

and to the general C/C++ programming community at large.

The point of this cross-posting is to open up the discussion to a

wider audience and to try and to figure out just what the package should

do and what the target audience might be. Right now, the discussion on

sci.math is slightly biased by the preponderance of mathematicians. Not

that this is a problem, but I'd like to see a wider audience of programmers

make some comments on what they'd like to see.

YOUR CONTRIBUTION

(1) If you've seen free C++ source for manipulating really large

integers, please let us know -- we've already heard about the

Gnu package written in C (I think it's called gmp?).

(2) There are a number of issues being raised about how the package

should behave, how it should be designed, what it should try and

do and not do, and so on, which you might be able to contribute

significantly to. I would personally like to get feedback from

a fairly diverse crowd since I think the package will ultimately

appeal to a *very* wide audience.

(3) There are some specific nitty-gritty issues currently being raised

about how to evaulate a/b or a%b when a and/or b are negative integers.

ANSI C does not define a standard behavior, and most compilers seem

to evaluate floor(a/b), for example, since this is what most CPUs

return. From a mathematical point of view, this is not necessarily

the most sensible behavior -- you would usually want to round a/b

towards zero. This has raised a number of issues which I think

deserves attention by a wider audience intimately familiar with

software engineering issues, C compilers, and mathematics.

Anyway, please feel free to jump into the fray. Follow-ups to this

thread will go to sci.math, comp.lang.c, and comp.lang.c++. I would

recommend, though, that you post followups to the original thread on

sci.math unless there's good reason to do otherwise. It makes sense

to me to try to keep a 'central' discussion wherever possible, and

that just happense to be where it is right now.

Hoping to hear from you soon!

--

roberto sierra

tempered microdesigns

san francisco, calif.

bert@netcom.com

--

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