Michael Everson wrote: > >(Remember that the empty set symbol really was an O with stroke, > >originally!) > > Surely a 0 with stroke, not a O with stroke.
The empty set sign was originally definitely the Norwegian/Danish letter CAPITAL O WITH STROKE. It never was related at all to a ZERO with stroke. See http://members.aol.com/jeff570/set.html (which I referred to earlier, though it unfortunately uses the term "null set"...; but it also (quite rightly) uses U+00D8 for the empty set symbol, rather than U+2205; the choice is stylistic): ---------------------------------------------------------- The null set symbol (�). Andr� Weil (1906-1998) says in his autobiography that he introduced the symbol: Wisely, we had decided to publish an installment establishing the system of notation for set theory, rather than wait for the detailed treatment that was to follow: it was high time to fix these notations once and for all, and indeed the ones we proposed, which introduced a number of modifications to the notations previously in use, met with general approval. Much later, my own part in these discussions earned me the respect of my daughter Nicolette, when she learned the symbol � for the empty set at school and I told her that I had been personally responsible for its adoption. The symbol came from the Norwegian alphabet, with which I alone among the Bourbaki group was familiar. The citation above is from page 114 of Andr� Weil's The Apprenticeship of a Mathematician, Birkhaeuser Verlag, Basel-Boston-Berlin, 1992. Translated from the French by Jennifer Gage. The citation was provided by Julio Gonz�lez Cabill�n. This letter is used in the Norwegian, Danish and Faroese alphabets. ------------------------------------------------------------ /kent k
