Re: [Bug-apl] Access to rational number numerator and denominator

[Christian Robert]

what is "bigints" ?

larger than ~62 bits or 9200000000000000000 ?

If so, I would agree 100%. Having a limit that is less than exact 64 bits 
(signed or unsigned)
is wrong. encode & decode can't manage more than ~62-~63 bits limit.


my 2 cents,
Xtian.

On 2017-08-28 22:33, Elias Mårtenson wrote:
> The true benefit of rational numbers is realised once there is support for 
> bigints. Jürgen has suggested that that is planned, and personally I can't wait.
>
> Regards,
> Elias
>
> On 29 August 2017 at 08:59, Frederick Pitts <address@hidden 
> <mailto:address@hidden>> wrote:
>
>     Louis,
>
>              Thanks for the quick response.
>
>              After working with the technique a bit, I observe that as long
>     as the rational number denominator is well within the range of integers
>     representable by floating numbers, 1 ∧ n returns the correct result.
>     But if the absolute value of the denominator exceeds 2 ⋆ 35, the
>     technique returns incorrect results.  For instance,
>
>            fiMax ← × / 53 ⍴ 2 ⍝ largest integer 53-bit f.p. mantissa holds
>            fiMax
>     ╔════════════════╗
>     ║9007199254740992║
>     ╚════════════════╝
>            1 ∧ fiMax ⍝ Correct result for fiMax
>     ╔════════════════╗
>     ║9007199254740992║
>     ╚════════════════╝
>            1 ∧ ÷ fiMax ⍝ Incorrect result. 1 is numerator of reciprocal.
>     ╔═╗
>     ║0║
>     ╚═╝
>
>              I was hoping to be able to access correct rational number parts
>     even when they approach the ⎕SYL[20;2] limit of 9200000000000000000.
>     It seems a shame to loose so much of the integer range because floating
>     point operations are sneaking into the numerator and denominator access
>     methods.
>
>     Regards,
>
>     Fred
>
>     On Tue, 2017-08-29 at 00:08 +0200, Louis de Forcrand wrote:
>      > Hi,
>      >
>      > No APL kb with me right now, sorry :(
>      >
>      > 1 LCM n
>      >
>      > gives the numerator of a fraction (floating or exact). If you need
>      > the denominator, do the same with the inverse of n. If you need both,
>      > for example:
>      >
>      > 1 LCM n POW 1 _1
>      >
>      > Cheers,
>      > Louis
>      >
>      > > On 28 Aug 2017, at 23:24, Frederick Pitts <address@hidden 
> <mailto:address@hidden>>
>      > > wrote:
>      > >
>      > > Hello,
>      > >
>      > >    Is there an existing mechanism for accessing rational number
>      > > numerator and denominator parts analogous to that for accessing
>      > > complex
>      > > number real and imaginary parts?  If yes, please let me know
>      > > how.  If
>      > > no, can a mechanism be implemented?
>      > >
>      > > Respectfully,
>      > >
>      > > Fred
>      > >
>      >
>      >