Hi, On Mon, May 5, 2014 at 7:49 PM, Takashi Kato <[email protected]> wrote:
> > Hi there, > > I'm wondering how should string-foldcase behave for capital sigma at the > end of word. For example, what should this return? (string-foldcase "XAOΣΣ") > > According to Unicode's CaseFolding.txt capital sigma is mapped to small > sigma. So this, I think and R6RS requires, should return "χαoσσ". However > R7RS doesn't specify it so could this be implementation dependent or if the > implementation supports Unicode it should respect it? > 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: The Unicode Standard prescribes special treatment of the Greek letter Σ, whose normal lower- case form is σ but which becomes ς at the end of a word. See UAX #29 [11] (part of the- Unicode Standard) for details. However, im- plementations of string-downcase are not required to pro- vide this behavior, and may choose to change Σ to σ in all cases. For the data files you can refer to SpecialCasing.txt for this rule. R6RS explicitly requires proper handling of final sigmas, not making this optional: http://www.r6rs.org/final/html/r6rs-lib/r6rs-lib-Z-H-2.html#node_sec_1.2 -- Alex
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