Iterators & Functionids

Hi, I try to get the following behaviour: test-action: [print "---" probe first iterator] test-predicate: [print type? list] forall-records object-list test-predicate test-action forall-records: func [list predicate action][ do predicate ; just for simple test ; iterate through the whole list of values ; check if the first entry satisfies the predicate ; if so execute the action forall list [if predicate [action]] ] I want to provide a predicate and an action that can use the parameters and local words. Of course the above code fails ** Script Error: list has no value What I came up with is a not so nice and IMO inflexible solution: forall-records: func [list predicate action][ if any [none? list empty? action][exit] ; iterate through the whole list of values ; check if the first entry satisfies the predicate ; if so execute the action forall list [if (predicate first list) [do action]] ] test-predicate: func [object][ either not none? (select object 'name) [true][false] ] forall-records object-list :test-predicate test-action I expect the first problem to be a binding problem. I read through the bindung stuff provided by Ladislaw but it's really hard... So how can the concept of C++ iterators, predicates, and functionids be implemented in Rebol? Did someone already wrote some generic functions for this? Robert

Hi Robert, On Tuesday, August 27, 2002, 11:24:11 AM, you wrote: RMM> Hi, I try to get the following behaviour: [...] What about: foreach-record: func ['word records predicate action] [ predicate: func reduce [word] predicate action: func reduce [word] action foreach record records [ if predicate record [action record] ] ]

>> list: [1 2 3 4 5 6 7 8 9]

>> foreach-record num list [even? num] [print num]

> -----Original Message----- > From: [rebol-bounce--rebol--com] [mailto:[rebol-bounce--rebol--com]] > ] > ]

Hi Robert, On Tuesday, August 27, 2002, 8:20:56 PM, you wrote: RMM> forall list [ RMM> object: first list RMM> if (do bind copy predicate 'list) [do bind copy action RMM> 'list] RMM> ] This way you are copying and rebinding the blocks at each cycle. Using functions is probably the best way, but if you prefer blocks you can: predicate: bind/copy predicate 'list action: bind/copy action 'list forall list [ object: first list if do predicate [do action] ] Regards, Gabriele. -- Gabriele Santilli <[g--santilli--tiscalinet--it]> -- REBOL Programmer Amigan -- AGI L'Aquila -- REB: http://web.tiscali.it/rebol/index.r

> -----Original Message----- > From: [rebol-bounce--rebol--com] [mailto:[rebol-bounce--rebol--com]] > cycle. Using functions is probably the best way, but if you > prefer blocks you can: