Re: [Scheme-reports] Strong win later reversed: Real numbers have imaginary part #e0

[Mark H Weaver <mhw@x>]

Alex Shinn <alexshinn@x> writes:
> This was revisited in item #286 in the 5th ballot, and
> we voted to revert the previous decision.

The results of #286 do not convince me that the working group changed
their minds about item #117.  #117 was a highly-focused ballot item on
this precise issue, whereas #286 was mostly about whether to add another
set of predicates.

This reversal poses onerous requirements on implementors, especially
those who wish to support R6RS as well.  The problem is that this
changes the domain of the following procedures:

  < > <= >= positive? negative?
  max min abs
  floor/ floor-quotient floor-remainder
  truncate/ truncate-quotient truncate-remainder
  quotient remainder modulo
  gcd lcm numerator denominator rationalize
  floor ceiling truncate round
  atan (two-arg version)
  make-rectangular make-polar

For example, this reversal means that (max 1.0+0.0i 1.0-0.0i) is
permitted, and the result is no longer uniquely determined.
What should the result be?

It also means that (modulo 5.0-0.0i 2.0-0.0i) is permitted.
What should the result be?

    Mark

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