Re: [Scheme-reports] Missing description of complex polar form

On 1 May 2011 23:49, Aaron W. Hsu <arcfide@x> wrote:

On Sat, 30 Apr 2011 20:30:14 -0400, Malcolm Tredinnick
<malcolm.tredinnick@x> wrote:

> Archaeological expeditions were similarly unrewarding — the current
> description of numbers has remained more or less unchanged since at
> least R4RS and the 1@1 style is not mentioned. One can kind of
> reverse-engineer the requirements from the hints in the description of
> (make-polar ...) and (angle ...) on page 29, but even there it doesn't
> explicitly tie the polar form to the x@y syntax!

The R6RS has a grammar description of the datum syntax for numbers which
includes the @ and normal complex forms. I don't know if any of this has
been used in the current report, but previous standards have provided
information on it. The TSPL also contains a more general description, but
my understanding was that this syntax was purposefully fairly vague.

If you mean the grammar specification in the <complex> production on page 13 of the R6RS report, then that's the same as in R7RS draft 1 and is similar all the way back to at least R4RS. However, the problem is that it's only describing a bunch of symbols, not semantics. That's not enough information for an implementer or for somebody wanting to verify correct behaviour. Nowhere is it mentioned that this *is* the polar form, for example, let alone whether the number after the "@" is interpreted as radians or degrees or even possibly pineapples.
You cannot come to a recent Scheme report and get any understanding of what 1@2 actually means.

If that's not the section you mean, could you provide a little specificity so I can see what I'm overlooking? I spent more than a little while looking through all the older reports and couldn't find the missing explanation of semantics.

Regards,
Malcolm