Re: [Bug-apl] Complex number display

[Frederick H. Pitts]

Elias,

        The part before the "Then:" states the obvious.  Numeric output
conversion converts numbers in internal format (implementation-defined))
to external literal decimal format.

        The part after the "Then:" is totally bogus.  What is the point of
performing complex number calculations and then summarily throwing away
the imaginary part?  The imaginary part could be the part the user is
interested in.

        Sincerely, I do not see anything here that legitimately contradicts the
descriptions cited in the IBM APL2 Language Reference.  The IBM document
says 1) display the real part as 0 if the real part magnitude is ⎕PP
orders of magnitude less than the imaginary part magnitude and 2)
suppress the display imaginary part if its magnitude is ⎕PP orders of
magnitude less than the real part.  The exception is when ⎕PP is at
maximum; then both parts are displayed at full precision.

Regards,

Fred

On Tue, 2014-05-20 at 12:47 +0800, Elias Mårtenson wrote:
> ISO/IEC 13751:2000 seems to give an implementation lots of flexibility
> here.
> 
> 
> I'm honestly not sure how to interpret this. Section 15.2.2 says:
> 
> 
>         Informal Description: Numeric output conversion converts
>         numeric values represented as numbers—numeric quantities whose
>         format is implementation-defined—into the same numeric
>         quantities represented in decimal notation as lists of
>         characters.
>
> 
> Then:
> 
> 
>         Note: Any imaginary-part of the numeric input to
>         Numeric-Output-Conversion is simply ignored; only the
>         real-part of a complex-number is used.
> 
> 
> Regards,
> Elias
> 
> 
> On 20 May 2014 12:24, Frederick H. Pitts <address@hidden>
> wrote:
>         Juergen,
>         
>                 Under "Display of Complex Numbers:" on page 13 of the
>         "APL2
>         Programming: Language reference", the document says:
>         
>                 "In J notation, the real or imaginary part is not
>         displayed if it is
>         less than the other by more than ⎕PP orders of magnitude
>         (unless ⎕PP is
>         at its maximum)".
>         
>                 In SVN 268, neither of the presented examples work.
>          The smaller
>         magnitude part is not zeroed if its the real part or
>         suppressed if its
>         the imaginary part.
>         
>                 In addition, complex numbers entered in polar notation
>         as described at
>         the top page 12 do not display correctly per the description
>         on page 13.
>         1D90 and 1R1.5707963267948965 should display as 0J1 assuming
>         ⎕PP is less
>         than maximum.  Currently the real part is displayed as some
>         number times
>         10 to the -16 power, i.e. zero for all intents and purposes.
>         
>         Regards,
>         
>         Fred
>         Retired Chemical Engineer
>         
>         
> 
>