To clarify the last point. Say each seq has a method to create an equivalent memoized seq, or return itself if memoization is not needed (e.g. in-range). Memoized seq returns a memoizing iterator, that first goes over previously calculated values, then starts storing newly calculated values in seq as it calculates them. Interface for this is a function stream-memoize :: seq -> seq. So
(let ([s2 (stream-map func s)]) (for ([i s2]) ...) (for ([i s2]) ...)) calculates all values twice (but does not use additional memory), but (let ([s2 (stream-memoize (stream-map func s))]) (for ([i s2]) ...) (for ([i s2]) ...)) only calculates values once. Eugene _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
