The main point is that asserting a general preference in an annotation for ∶ to express a ratio, as Asmus had in his formulation, is simply wrong and counterproductive. (We are not going to change the world's usage from : to ∶ by fiat; and and the glyphic difference is quite subtle, and missing in a great many fonts. Compare that with the difference between hyphen-minus and minus, which is much more pronounced, and much better carried across fonts.)
The most that we could say is that in certain mathematical contexts ∶ is preferred to : for expressing ratios, not that it is generally preferred. By the way, here's your list with visible characters instead of the U+'s. - HYPHEN-MINUS − MINUS SIGN / SOLIDUS (Unicode 1.0 called it "SLASH") ∕ DIVISION SLASH \ REVERSE SOLIDUS (Unicode 1.0 called it "BACKSLASH") ∖ SET MINUS * ASTERISK *// you had U+003A = : instead of *.* ∗ ASTERISK OPERATOR ◦ WHITE BULLET ∘ RING OPERATOR • BULLET ∙ BULLET OPERATOR | VERTICAL BAR ∣ DIVIDES ‖ DOUBLE VERTICAL BAR ∥ PARALLEL TO : COLON ∶ RATIO ~ TILDE ∼ TILDE OPERATOR · MIDDLE DOT ⋅ DOT OPERATOR ------------------------------ Mark <https://plus.google.com/114199149796022210033> * * *— Il meglio è l’inimico del bene —* ** On Tue, Jul 10, 2012 at 5:05 PM, Ken Whistler <[email protected]> wrote: > On 7/10/2012 4:22 PM, Mark Davis ☕ wrote: > > I would disagree about the preference for ratio; I think it is a > historical accident in Unicode. > > > Not really. > > The following pairs dating from Unicode 1.0 were deliberate: > > U+002D HYPHEN-MINUS > U+2212 MINUS SIGN > > U+002F SOLIDUS (Unicode 1.0 called it "SLASH") > U+2215 DIVISION SLASH > > U+005C REVERSE SOLIDUS (Unicode 1.0 called it "BACKSLASH") > U+2216 SET MINUS > > U+003A ASTERISK > U+2217 ASTERISK OPERATOR > > U+25E6 WHITE BULLET > U+2218 RING OPERATOR > > U+2022 BULLET > U+2219 BULLET OPERATOR > > U+007C VERTICAL BAR > U+2223 DIVIDES > > U+2016 DOUBLE VERTICAL BAR > U+2225 PARALLEL TO > > U+003A COLON > U+2236 RATIO > > U+007E TILDE > U+223C TILDE OPERATOR > > U+00B7 MIDDLE DOT > U+22C5 DOT OPERATOR > > If anything, the "accident" is that the use of "!" for factorial was not > distinguished with a separate symbol character. I don't recall the > argument in detail -- it was discussed. But I suspect that it came down > to most of the math operators being in principle distinguishable because > they are rendered on the math centerline, rather than the baseline, > whereas nobody could think of a good reason for a layout distinction > for the factorial -- so it fell instead into the bucket already occupied > by "." as full stop versus decimal point (versus record separator > versus...) > > Now subsequent history has since led to more systematic distinctions, > both in use and in glyph design, for some of the pairs listed above. > For example, the two tildes generally look different. The SET MINUS was > discovered to actually be distinct from a backslash, with a different > angle and length. And so on. So that has whittled down the list of > characters that people, after the fact, come to think of as accidental > duplicates. > > But trying to rationalize these decisions by examining only the latest > charts, while ignoring the history of how these distinctions came about > in the first place is not a productive direction, IMO. > > Incidentally, one of the reasons the set of symbols in the U+2200 > Mathematical Operators block got a somewhat different treatment than > generic punctuation or other symbols or combining marks, when it comes > to unification versus non-unification decisions back in the original > draft charts in 1989 and 1990 had something to do with the intuition > back then that having unambiguous encodings for the math operators > would be important for machine processing of mathematical data > (as in algebra systems). It isn't so clear now, in retrospect, whether > some of the disunifications were a good idea or not. But those > decisions are what we have inherited in the standard now, for better > or worse. > > --Ken > > > > >
