~~ is the fix! Thanks. This is ringing a bell. I just went looking through some notes from last year, and found something about using ~~ (but not \ ) to escape special characters. I was using Perl to process string answers. I'm all set.
Good to know I don't have to load calc when I've already got the circuits.logic.US tikz library going.
Good to know I don't have to load calc when I've already got the circuits.logic.US tikz library going.