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

Simon Marlow marlowsd at gmail.com
Mon Apr 19 09:37:54 EDT 2010

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.


> 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
> 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
> 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
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