Alan Wood wrote:
When I prepared the proposal for U+23D0 ⏐ VERTICAL LINE EXTENSION, it was indeed to ensure the complete representation of some other character set in Unicode. My target was actually the PUA usage defined by Adobe, which included what's needed for "the" Symbol font.I think this leaves only one character in the old Symbol font that does not have a Unicode equivalent:
RADICAL EXTENDER (decimal 96 in the Windows version)
I did not consider perfect round tripping a necessity: it was enough for me to allow the conversion of old data to Unicode, and to leave the old world behind. Nor do I consider having a perfect handling of symbol pieces in a Unicode only world a necessity: exchanging with somebody the plain text "...U+23B2 ⎲ SUMMATION TOP U+23B3 ⎳ SUMMATION BOTTOM ... " does not improve one bit our communication over exchanging "...U+2211 ∑ N-ARY SUMMATION..." Nor do I consider symbol pieces a good solution for typesetting (*glyphs* for the symbol pieces may be a good thing for that problem, but that requires more communication between a layout engine and a font than a mapping from characters to glyphs).
For the RADICAL EXTENDER, I could not convince myself that such a character was needed; U+23AF ⎯ HORIZONTAL LINE EXTENSION is a fine character to use for that purpose. U+23D0 ⏐ VERTICAL LINE EXTENSION was much easier to justify (i.e. nothing else made sense) and there was the model of U+23AF ⎯ HORIZONTAL LINE EXTENSION to build on.
This represents only my opinion, and explains why I did not propose RADICAL EXTENDER. It says nothing about how the UTC would react to such a proposal.
Eric.
