^- @ 42
a type is the shape a value can have.
@ is the atom type, and ^- casts a value to a type: it names the type and checks the value fits.
glossary
^- 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 ^-