RE: [Jython-dev] complex calculation

[Tim P. <ti...@ho...>]

[Pilho Kim]
> [Result on Python 2.0]
> (2+1j)^55 = (1.55453313831e+019+5.99152971656e+018j)
>
> [Result on Jython 2.0 or Jython 2.1 alpha 1]
> (2+1j)^55 = (9223372036854775807+5991529716557069312j)

[Finn Bock]
> I think I have tracked it down to PyComplex.toString():
>
>     public static String toString(double value) {
>         if (value == Math.floor(value)) {
>             return Long.toString((long)value);
>         } else {
>             return Double.toString(value);
>         }
>     }
>
> Changing that method to:
>
>     public static String toString(double value) {
>         if (value == Math.floor(value) &&
>               value < Long.MAX_VALUE && value > Long.MIN_VALUE) {
>             return Long.toString((long)value);
>         } else {
>             return Double.toString(value);
>         }
>     }
>
> seems to work for the test program, but my understanding of the finer
> points of FP and complex numbers is zero.

Take heart!  Mine isn't, and I'm sure you've nailed it, except *perhaps* for
wanting <= and >= instead of < and >.

The original bare "value == Math.floor(value)" test is a common
floating-point coding mistake, and across languages:  the author always has
in mind, for example, distinguishing 3.1 from "3.0 on the nose", but doesn't
realize that, e.g., floor(1e300) == 1e300 too (every f.p. number with a "big
enough" exponent is an exact integer!).

no-wonder-they-call-it-"complex"<wink>-ly y'rs  - tim