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Various dot types for multiplication #169

Open skalee opened 3 years ago

skalee commented 3 years ago

Sometimes multiplication is denoted with a small dot. At least two types of dot are used:

They look almost identical and I suppose the are completely interchangeable. Notifying @ronaldtse just in case I'm wrong.

ronaldtse commented 3 years ago

Good find. Ping @opoudjis for thoughts.

opoudjis commented 3 years ago

I know from my own discussions with Unicode staff, 20 years ago, that they have long been sick of the profusion of dots.

https://www.w3.org/TR/html4/sgml/entities.html

<!ENTITY sdot     CDATA "&#8901;" -- dot operator, U+22C5 ISOamsb -->
<!-- dot operator is NOT the same character as U+00B7 middle dot -->

https://codepoints.net/U+00B7 https://codepoints.net/U+22C5 https://tex.stackexchange.com/questions/19180/which-dot-character-to-use-in-which-context

"Note that Unicode now states "preferred to 00B7 · for denotation of multiplication" as an informative note on 22C5 ⋅. This is certainly consistent with the above answer."

From what I'm gathering, the correct symbol is sdot, but everybody defaults to middot (including, I am embarrassed to say, me, in asciimath2unitsml), because they don't realise that sdot is the proper multiplication symbol.

Asciimath and TeX both map \cdot to 22C5. So I think it's fine to canonically map middot to sdot in whatever you are doing, although most people won't notice.

skalee commented 3 years ago

Old Electropedia uses both characters, I suppose depending on who has authored given concept. I am glad to hear confirmation that in context of mathematical formulas they both mean exactly the same, though it's misuse of middot. Thanks a lot!

Asciimath and TeX both map \cdot to 22C5. So I think it's fine to canonically map middot to sdot in whatever you are doing, although most people won't notice.

I am going to convert these to AsciiMath or LaTeX, therefore normalization makes sense.