Iteration

(for-each proc! lst): Standard Higher-Order List Procedure. Apply proc! to each element of the given list. Called primarily for side effects.
(repeat i proc!): Extended Scheme Procedure. Call proc! (a zero-parameter procedure, a.k.a., a “thunk”) i times.
(repeat i proc! val): Extended Scheme Procedure. Evaluate (proc! val)i times.
(repeat i proc! v₁ ... v_n): Extended Scheme Procedure. Evaluate (proc! v₁ ... v_n)i times.