Ah, nice :) Thanks! martin
On Tue, Jul 20, 2010 at 8:39 PM, Jos Koot <[email protected]> wrote: > Yet another one using -apply-: > > (define (same-parity x . xs) > (cond > ((null? xs) (list x)) > ((equal? (even? x) (even? (car xs))) (cons x (apply same-parity xs))) > (else (apply same-parity x (cdr xs))))) > > Jos > >> -----Original Message----- >> From: [email protected] >> [mailto:[email protected]] On Behalf Of Martin DeMello >> Sent: 20 July 2010 15:37 >> To: PLT-Scheme Mailing List >> Subject: [racket] sicp exercise 2.20 >> >> By way of a puzzle, I've been trying to solve SICP exercise 2.20 >> ---------------------------- >> Using the (define (f x . args)) notation, write a procedure >> "same-parity" that takes one or more integers and returns a >> list of all the arguments that have the same even-odd parity >> as the first argument. For example, (same-parity 1 2 3 4 5 6 7) >> (1 3 5 7) >> (same-parity 2 3 4 5 6 7) >> (2 4 6) >> ---------------------------- >> using "straight recursion", that is, without using any `let` >> or `define` constructs. Still not managed to find the trick >> that will tack on the first argument as the head of the list. >> Anyone have a hint? >> >> martin >> _________________________________________________ >> For list-related administrative tasks: >> http://lists.racket-lang.org/listinfo/users > > > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
