(mul (add 1 2) (add 3 4))
a call can nest on both arguments.
glossary
%: calls a gate with several arguments, gathering them into one sample.
%:(add 2 3) is 5.
irregular forms:
(gate a b c) is %:(gate a b c)
mul multiplies two atoms.
(mul 3 4) is 12.
add sums two atoms.
(add 2 3) is 5.