Case transformations in strings

Maciej Stachowiak mjs at apple.com
Fri Mar 6 09:05:23 PST 2009


On Mar 4, 2009, at 11:35 AM, Allen Wirfs-Brock wrote:

> Any input from our other Unicode experts would be appreciated...
>
> Here's what I found (running on Windows Vista):
> IE, FF, Opera
> "\u00DF".toUpperCase()  returns "\u00DF"
> Safari, Chrome
> "\u00DF".toUpperCase()  returns "SS"
>
> It would be interesting if somebody could try the above for FF and  
> Opera on a non-Windows machine to check whether this is a byproduct  
> of using the Windows provided conversion routines.
>
> Question 1: Is the specified length invariant essential or just  
> noise in the ES3 spec. If it's not we could could eliminate that  
> invariant and say that each S character is replaced in the result by  
> the corresponding character(s) from the Unicode case mappings.

I don't think the invariant is essential. Or at least, I don't know of  
other parts of the spec depending on it, or Web compatibility  
requiring it. Having this requirement prevents doing the right thing  
Unicode-wise. I think the spec needs at least allow doing the right  
thing, therefore I think the string length requirement should be  
removed.

It may be more problematic at this time to mandate doing the right  
thing.

  - Maciej

>
>
> Question 2: If the observed variance is indeed a result of using the  
> Windows mapping do we really want to require every implementation to  
> provide its own internal mappings data and algorithms (as Safari and  
> Chrome may be doing) if the underlying host is not fully Unicode  
> compliant?
>
> Question 3: Do we need to explicitly provide for some implementation  
> variance here.  That appears to be the current reality of the web.   
> Do we want to try to stamp out the variance or to acknowledge and  
> allow it.
>
> Question 4: Is Chrome correct with:
> "\u03A3\u03A3".toLowerCase() == σς, not σσ
> And everybody else is wrong?  This sounds like a reasonable  
> interpretation of the explicit mention of SpecialCasing.txt in the  
> note (but that the note is not normative). If so, should be explicit  
> mention in step 3 that the translation must be appropriately context  
> sensitive.
>
> Finally, is any of the above going to actually influence anything.   
> If not, maybe carrying the exact ES3 specification forward is ok.
>
> Allen
>
>
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