Re: [racket-users] For/lists: where is #:continue?
I think you're looking for #:when / #:unless. On Mon, Jul 13, 2015 at 3:12 PM, Pekka Niiranen pekka.niira...@pp5.inet.fi wrote: Hello users, What is the proper design pattern to skip invalid values when using for/list? The programs below fails because #:continue is not recognized: for/list ([i (in-range 0 1000)]) (let ((value (vector-ref vector i))) (if ( 0 (length value)) value #:continue))) Sure, I could bypass this limitation by building the list explicitely with plain for + cons or: (define result-list (for/list ([i (in-range 0 1000)]) (let ((value (vector-ref vector i))) (if ( 0 (length value)) value empty = then filter empties from result-list with another loop... -pekka- -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] For/lists: where is #:continue?
Also, since you're not actually interested in the value of i, you should probably use in-vector rather than in-range. The whole example would be: (for/list ([value (in-vector vector)] #:when ( 0 (length value))) value) On Mon, Jul 13, 2015 at 3:18 PM, Jon Zeppieri zeppi...@gmail.com wrote: I think you're looking for #:when / #:unless. On Mon, Jul 13, 2015 at 3:12 PM, Pekka Niiranen pekka.niira...@pp5.inet.fi wrote: Hello users, What is the proper design pattern to skip invalid values when using for/list? The programs below fails because #:continue is not recognized: for/list ([i (in-range 0 1000)]) (let ((value (vector-ref vector i))) (if ( 0 (length value)) value #:continue))) Sure, I could bypass this limitation by building the list explicitely with plain for + cons or: (define result-list (for/list ([i (in-range 0 1000)]) (let ((value (vector-ref vector i))) (if ( 0 (length value)) value empty = then filter empties from result-list with another loop... -pekka- -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [racket-users] For/lists: where is #:continue?
In that case, you probably want to make use of in-value to bind single-value sequences in your for*/list: (for*/list ([(start end) (in-parallel 1 1000)] [i (in-range start (sub1 end))] [s (in-value (vector-ref vector i))] [columns (in-value (string-split s ,))] [col# (in-value (length columns))] #:when ( 2 col#)) (first columns)) On Mon, Jul 13, 2015 at 3:46 PM, Pekka Niiranen pekka.niira...@pp5.inet.fi wrote: Hello Sir. all true, but my example was bad simplification from the original code. The ugly part is to insert the multi-step function into #:when -clause and in case of success use function's internal parameter (columns) only. My imperative mind wants to use continue in the place empty below: (for*/list ([(start end) (in-parallel 1 1000)] [i (in-range start (sub1 end))]) (let* ((columns (string-split (vector-ref vector i) ,)) (col# (length columns))) (if ( 2 col#) (first columns) empty))) On 7/13/15 10:26 PM, Jon Zeppieri wrote: Also, since you're not actually interested in the value of i, you should probably use in-vector rather than in-range. The whole example would be: (for/list ([value (in-vector vector)] #:when ( 0 (length value))) value) On Mon, Jul 13, 2015 at 3:18 PM, Jon Zeppieri zeppi...@gmail.com wrote: I think you're looking for #:when / #:unless. On Mon, Jul 13, 2015 at 3:12 PM, Pekka Niiranen pekka.niira...@pp5.inet.fi wrote: Hello users, What is the proper design pattern to skip invalid values when using for/list? The programs below fails because #:continue is not recognized: for/list ([i (in-range 0 1000)]) (let ((value (vector-ref vector i))) (if ( 0 (length value)) value #:continue))) Sure, I could bypass this limitation by building the list explicitely with plain for + cons or: (define result-list (for/list ([i (in-range 0 1000)]) (let ((value (vector-ref vector i))) (if ( 0 (length value)) value empty = then filter empties from result-list with another loop... -pekka- -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups Racket Users group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
