Manipulating Expressions
	• E — expression, u — expression variable • box E — term, x — term variable • let box u = M in N — substitute expression denoted by M for u in N • embed(x) = let box u = x in box (...u...) • eval(x) = let box u = x in u • simplify(x) = case x of box (0*u) Þ box (0) | ...