(load "digital-circuits.txt") (define the-agenda (make-agenda)) (define inverter-delay 2) (define and-gate-delay 3) (define or-gate-delay 5) (define input-1 (make-wire)) (define input-2 (make-wire)) (define sum (make-wire)) (define carry (make-wire)) (probe 'sum sum) (probe 'carry carry) (half-adder input-1 input-2 sum carry) (set-signal! input-1 1) (propagate) (set-signal! input-2 1) (propagate)