Thought for the Day!
Halmos . . . .
most nearly immortal contributions are
an abbreviation and a typographical symbol.
I invented "iff" for
"if and only if" --but I could never believe that I was really its
first inventor. . . . . .
The symbol is definitely not my invention - it
appeared in popular magazines (not mathematical ones) before I adopted
it, but once, again, I seem to have introduced it into
mathematics. It is the symbol that sometimes looks like , and
is used to indicate an end, usually the end of a proof. It is
most frequently called the 'tombstone', but at least one generous
author referred to it as the 'halmos'."
From I Want to Be a
Mathematician: An Automathography,
by Paul Halmos,