Takashi Kato scripsit:

> > According to Unicode's CaseFolding.txt capital sigma is mapped to small
> > sigma. So this, I think and R6RS requires, should return "χαoσσ".

That's correct.

> > R7RS doesn't specify it so could this be implementation dependent or if the
> > implementation supports Unicode it should respect it?

The implementation must respect it, whether it implements all of Unicode
or not.  That is, if both Σ and σ are permitted in strings, then
(string-foldcase "XAOΣΣ") must evaluate to "χαoσσ".  In this case,
Unicode, R6RS, and R7RS all say the same.

Alex Shinn scripsit:

> R7RS specifies this in section 6.7, saying it uses the "Unicode full
> string [...] lowercasing and case-folding algorithms."  It goes on to
> clarify this case specifically as optional:

In string-foldcase the behavior is prescribed.  In string-downcase,
it is optional:  (string-downcase "XAOΣΣ") must evaluate to either
"χαoσς" (full Unicode support) or "χαoσσ" (as permitted by R7RS).

(Note that in normal Greek-language text, a word never ends in two
consecutive sigmas.)

--
John Cowan          http://www.ccil.org/~cowan        cowan@ccil.org
Business before pleasure, if not too bloomering long before.
        --Nicholas van Rijn

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