(define make-ra-stack (lambda () (make-ra-stack-with-at-most 8))) ; choose your own constant (define make-ra-stack-with-at-most (lambda (max-height) (let ((header (make-vector 2)) (cells (make-vector max-height))) (vector-set! header 0 0) ; height (vector-set! header 1 cells) ; stack itself header)))Note that only the header is returned, because the actual cells are accessed through it.