way***. If we use the proper Unicode operator ∘, then let's make a wiki page for all the common OSes/input methods, saying how to input it (aside from copy/paste). Is there anything on the Web somewhere already? Did Perl do this ( - I think they introduced some Unicode-based syntax)? There's http://www.haskell.org/haskellwiki/Unicode-symbols , which has some information (none of which let me write ∘ in an e-mail without using copy/paste).
Most platforms have some way to define new keys: on Unix with X11 you can use Xkb or xmodmap (the keysym for a Unicode character is the codepoint expressed as a hex constant, so 0x2218 for ∘), and there are a handful of Xkb editors out there; on OS X you can use keyboard substitutions (Language & Text > Text) or use a program such as Ukelele to modify the keyboard layout; I don't know specifics for Windows, but at its lowest level there are registry tweaks and there should also be programs to do those tweaks in people-comprehensible ways.