!!
=/ f |= a=@ ^- @ (mul a a) (f 6)

a gate can cast its product with ^-.

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=@.

^- casts a value to a named type: it checks the value fits and relabels it.

^-(@ 42) is 42.

irregular forms:

a leading backtick cast - the type in backticks, then the value - is ^-

%: 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.