[fpc-pascal] Division by Zero: EDivByZero and EZeroDivide

[Jorge Aldo G. de F. Junior]

Wouldnt a NaN (Not a number) be more "matematically correct" result (I saw
that on an old book about i387)

Matematically division by zero is an "mathematical impossibility", so NaN
would be more logical

Is there a way to deal with NaN's and other i387 (and similars) conventions
directly in Pascal ?

Something like :

If A / B = NaN then something();

2009/10/18 Tom Verhoeff <T.Verhoeff at tue.nl>

> On Sat, Oct 17, 2009 at 01:57:28PM +0200, Bart wrote:
> >
> > Is there a reason why in fpc both floating point and integer division
> > by zero raise an EDivByZero exception?
> >
> > See: http://docwiki.embarcadero.com/VCL/en/SysUtils.EZeroDivide
> >
> > SysUtils.EZeroDivide exception is raised when an application attempts
> > to divide a floating-point value by zero.
> > Note:  Integer divide-by-zero errors raise the SysUtils.EDivByZero
> exception.
>
> It would be nicer if one had the ability to make floating-point division
> by zero return an IEEE 754 plus/minus infinity, without raising an
> exception.  This is e.g. useful when one needs to evaluate rational
> functions.  Without such an infinity, you need to make a nasty case
> analysis, which furthermore depends on the rational function.
>
> A simple example is the situation where one needs to calculate
> the replacement resistor value R for parallel resistors having
> values R1, R2, ..., Rk.  The formula is R = 1/(1/R1 + 1/R2 + ... + 1/Rk).
> The formula gives a divide-by-zero if one of the resistors has value 0.
> But in that case, the replacement value R also equals 0.  When allowing
> infinities, it just works out fine (infinity + x = infinity, 1/infty = 0).
> That is precisely why IEEE 754 has infinities.  Also see
>
>        <http://www.cs.berkeley.edu/~wkahan/ieee754status/why-ieee.pdf<http://www.cs.berkeley.edu/%7Ewkahan/ieee754status/why-ieee.pdf>
> >
>
> for other examples and further motivation.
>
> Unfortunately, many compilers still do not fully support the IEEE 754
> floating-point standard.
>
> Best regards,
>
>        Tom
> --
> E-MAIL: T.Verhoeff @ TUE.NL     | Dept. of Math. & Comp. Science
> PHONE:  +31 40 247 41 25        | Technische Universiteit Eindhoven
> FAX:    +31 40 247 54 04        | PO Box 513, NL-5600 MB Eindhoven
> http://www.win.tue.nl/~wstomv/ <http://www.win.tue.nl/%7Ewstomv/>  | The
> Netherlands
> _______________________________________________
> fpc-pascal maillist  -  fpc-pascal at lists.freepascal.org
> http://lists.freepascal.org/mailman/listinfo/fpc-pascal
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freepascal.org/pipermail/fpc-pascal/attachments/20091018/207fa250/attachment.html>