charged

Code is Data that is charged.

Charging depends on assignment:
f : now # uncharged data, evaluated only when f() or f! occurs, or via full evaluation with !!
f := now # semi charged := evaluated upon normal evaluation of the parent context
def f:{now()} # charged code, evaluated upon partial evaluation of the parent context
f = now # charged symbol/variable: evaluated to the time whenever the symbol f occurs
f = now # resolved to current time immediately in the REPL, or whenever f! occurs

See evaluation for details.