Unicode alternative for '..' (ticket #3894)

[Simon Marlow]

On 15/04/2010 18:12, Yitzchak Gale wrote:
> My opinion is that we should either use TWO DOT LEADER,
> or just leave it as it is now, two FULL STOP characters.

Just to be clear, you're suggesting *removing* the Unicode alternative 
for '..' from GHC's UnicodeSyntax extension?

I have no strong opinions about this and I'm happy to defer to those who 
know more about such things than me.  The current choice of MIDLINE is 
probably accidental.

Cheers,
	Simon



> Two dots indicating a range is not the same symbol
> as a three dot ellipsis.
>
> Traditional non-Unicode Haskell will continue to be
> around for a long time to come. It would be very
> confusing to have two different visual glyphs for
> this symbol.
>
> I don't think there is any semantic problem with using
> TWO DOT LEADER here. All three of the characters
> ONE DOT LEADER, TWO DOT LEADER, and HORIZONTAL
> ELLIPSIS are legacy characters from Xerox's XCCS.
> There, the characters they come from were used for forming
> dot leaders, e.g., in a table of contents. Using them that way
> in Unicode is considered incorrect unless they represent text
> that was originally encoded in XCCS; in Unicode, one does
> not form dot leaders using those characters. However, other
> new uses are considered legitimate. For example, HORIZONTAL
> ELLIPSIS can be used for fonts that have a special ellipsis glyph,
> and ONE DOT LEADER represents mijaket in Armenian encodings.
> So I don't see any reason why we can't use TWO DOT LEADER to
> represent the two-dot range symbol.
>
> The above analysis is based in part upon a discussion of these
> characters on the Unicode list in 2003:
>
> http://www.mail-archive.com/unicode@unicode.org/msg16285.html
>
> The author of that particular message, Kenneth Whistler, is
> of the opinion that two dots expressing a range as in [0..1]
> should be represented in Unicode as two FULL STOP characters,
> as we do now in Haskell. Others in that thread - whom
> Mr. Whistler seems to feel are less expert than himself
> regarding Unicode - think that TWO DOT LEADER is appropriate.
> No one considers replacing two-dot ranges with HORIZONTAL
> ELLIPSIS.
>
> If we can't find a Unicode character that everyone agrees upon,
> I also don't see any problem with leaving it as two FULL STOP
> characters.
>
> Thanks,
> Yitz
> _______________________________________________
> Glasgow-haskell-users mailing list
> Glasgow-haskell-users at haskell.org
> http://www.haskell.org/mailman/listinfo/glasgow-haskell-users