[swannodette]

It's interesting to note that a big reason ( ) dominate in Lisp here is that pg adopts the FP habit of short var names. If anything this is probably just a measure of the tendency to use long vs short name - mainstream OO practice encourages the former. It would be interesting to rerun the heatmap for Lisp with a typical CLOS program. I think you'll find that ( ) no longer dominate.

EDIT: And in fact here's a heatmap of core.logic (1K LOC) which is fairly OO-ish in its design - http://twitpic.com/6hwj88. ( ) are strong but do not dominate everything.

UPDATE: And here's a 1.4K LOC Clojure program, core.match http://twitpic.com/6hwo8w/full. ( ) again do not dominate.