adding machine/tally mode

[bobbagwill]

I would like an adding machine mode, where you enter a number and hit enter, and you get a running total. Some desirable sub-modes would be: - tally mode (just hit enter to increment tally) - integer mode (limit to integral input) - money (decimal) input

A fancier tally mode would let you assign a key to a variable, so if you were counting sheep and goats, you could press S to increment sheep and G to increment goats.