!!
=/ g |= n=@ (mul 2 n) =/ d |_ n=@ ++ $ (mul 2 n) -- (add (g 3) (d 4))

a gate is a door whose sample you replace on every call.

glossary

=/ pins a named value (a face) into the subject for the lines below it.

name=value optionally declares the type.

=/(a 3 (add a a)) is 6.

|= makes a gate: a function with one named sample, then a body.

the body runs with the sample bound.

call the gate to run it.

(|=(a=@ (add a 1)) 4) is 5.

$= wraps a mold with a face, naming the value it produces.

$=(x @) is the mold x=@.

%: 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.

|_ makes a door: a core carrying a sample, with many named arms.

~(arm door value) sets the sample, then pulls that arm.

a door is a gate with many named entry points.

=/  d
  |_  n=@
  ++  inc  (add n 1)
  --
~(inc d 4)

is 5.

add sums two atoms.

(add 2 3) is 5.