Iterators

S is a collection

Elements(S) = {e₁, e₂, …, e_n} where n ≥ 0

∀ e ∈ Elements(S), ∃ I′ : iterator_next( I₀ ) → I′

Unary function

F (x): Domain → Codomain

binary function

F (x, y): Domain₁ × Domain₂ → Codomain

unary predicate

P (x): Bool

binary predicate

P (x, y): Bool