More-than-ASCII chars

MJ Ray wrote:

> I recently ran into the problem with the PLT Scheme edition's
> ssax:xml->sxml hitting a UTF-8 numeric ᤓ IMO, the real bug is
> that PLT's integer->char doesn't handle anything over 255, but could
> that sort of entity be handled in another way?

The current version of SSAX (tagged in the repository with the
RELEASE_4A_PT tag) no longer uses integer->char or other similar
functions. Instead, SSAX relies on the functions provided in a module
char-encoding.scm. In particular, functions ascii->char and
ucscode->char. The char-encoding.scm module is of course platform
specific, unfortunately. Each platform should provide its own
implementation of these functions. Scheme48 has a native ascii->char;
Bigloo has ucs2->char. I think Gauche has something similar too. Any
Java/JVM-based Scheme system should have no problem with implementing
these functions. However, until we have a character set SRFI,
char-encoding.scm will remain platform-specific. Perhaps some of the
readers of this list would like to take upon that SRFI?

Actually, SSAX makes one more implicit assumption, that Scheme's
char-alphabetic? function will return #t for all characters that the
XML Recommendation says are alphabetic. char-alphabetic? will for sure
return #t for any alphabetic ASCII character. If char-alphabetic?
supports other encodings, and if that predicate can correctly
distinguish an alphabetic character from a punctuation in these
encodings is unclear. Perhaps on some systems that handle Unicode/UCS2
char-alphabetic? can do all that. If it can, SSAX can handle XML
documents where _tag_ names themselves (not the character content!)
are written in Greek, in Kana, or Kanji.  Indeed, according to the XML
Recommendation, all Kanji are considered letters and may appear
wherever an ASCII letter is allowed.





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