Alex Shinn <alexsh...@gmail.com> writes:
> For exponentiation, R[34]RS noted the convention
> "0^0 is defined to be equal to 1."
>
> R5RS clarified this as "0^z is 1 if z = 0 and 0 otherwise."
>
> R6RS changes this to:
>
> (expt z1 z2) procedure
>
> Returns z1 raised to the power z2. For nonzero z1, this is
> e^{z2 log z1}. 0.0^z is 1.0 if z = 0.0, and 0.0 if (real-part z) is
> positive. For other cases in which the first argument is zero,
> either an exception is raised with condition type
> &implementation-restriction, or an unspecified number object is
> returned.
>
> As a minor issue, it replaced the exact numbers with
> inexact numbers, although all but one of the zero base
> examples are exact. I'm assuming this was a stylistic
> change, and that from the examples the intention is the
> rule applies to any base which answers #t to `zero?'.
>
> What I'm more interested in is the unusual behavior
> that the result _either_ raises an exception _or_ returns
> an unspecified number. I believe this is the only place
> in any of the reports where the semantics is the disjunction
> of signalling an error and an unspecified value. What's
> the story behind this?
This is where we made the change:
https://bitbucket.org/sperber/r6rs/changeset/3641c2841e1bc34d5fbf8946876eab015e132870
changeset: 697:3641c2841e1b
user: clinger
date: Thu Aug 24 21:12:37 2006 +0000
summary: Minor revisions to base.tex (generic arithmetic).
Unfortunately, I can neither remember how that came about, nor can I
find any mention of it in the minutes. Maybe Will remembers more.
--
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla
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