Hi Jean-Louis, first: thank you very much for your instructive post!
On 05.06.2011 19:49, Jean-Louis Faucher wrote: > > 2011/6/5 Rony G. Flatscher <rony.flatsc...@wu-wien.ac.at > <mailto:rony.flatsc...@wu-wien.ac.at>> > > would it be possible to have the REPLY keyword statement for routines? > > If I remove the test context->inMethod() then reply *seems* to work > from a ::routine (tested with a tiny script). > But this is not a proof that it would work all the times. > It crashes when called from an internal routine. > > > There are quite a few cases, where using routines and multithreading > would seem to be easier to comprehend and to apply, if REPLY was > available for routines. > > A good old class method is almost as simple as a ::routine. I don't > see any gain of functionality if we allow to reply from a ::routine, > unless we allow also to expose some variables from a ::routine. For you, Rick, other Java/C++-savvy programmers and myself: yes. However, what appears so easy for us, is not necessarily easy for others, for whom creating "a good old class method" is a high barrier, inhibiting (due to steep learning curves, time/resource-pressure etc.) actually taking advantage of it for their problems. So a *no* (about easily creating a class method) for programmers who are not acquainted with OO or have no experience/need creating their own classes for solving their problems. For this (in my environment rather large) group, this question is one of usability! It is much easier for this group to kick off multithreading via a REPLY from within a routine. For this group this in itself would be very helpful and valuable functionality, if this multithreading was made available for routines (if at all possible in a reliable way). ooRexx is (should be) philosophically following Rexx in its principles (like human-centricness, dynamic typing, non-signature-based interfaces etc.). > > [digression] > > Instructions that can be called only from methods : > > expose : I still don't understand why it's not possible to expose > variables from a ::routine... > If we do a relation with > - anonymous inline functions (often called lambda or block), > - outer environment (the variables used by the lambda, which are not > parameters), > - and closure (which is the outer environment which remains associated > to the lambda, even when the lambda is called outside the definer's > scope), > then the exposed variables would be the variables to retain in the > closure. > Most of the languages don't require to declare the variables to > capture, but C++ lets /optionally/ declare them, and that remind me > the functionality of our expose : > ----- c++ > std::vector<int> some_list; > int total = 0; > std::for_each(some_list.begin(), some_list.end(), [&total](int x) { > total += x; }); > ----- oorexx (with extensions) > some_list = .array~of.. > total = 0 > some_list~each([expose total; total += arg(1)]) > ----- > C++ lets capture a variable by value or by reference. In ooRexx, > expose is always by reference, right ? Currently, only internal > procedures allow to expose variables, but internal procedures can't be > manipulated like routines... > In the example above, there is a need of closure, because the lambda > is called in the context of the 'each' method, which is not the > context of the definer (i.e. 'each' does not - and could not - expose > the 'total' variable). > > > forward : nothing to say > > > guard : in relation with the object variables dictionary (ovd). I > don't know if the routines have a similar concept like caller > variables dictionary (cvd ?). And I don't know if that would make > sense to manage synchronisation on this cvd. Probably yes, > synchronisation would be necessary if we allow > - reply and expose in ::routine > - expose and closure (even if no reply in ::routine, because thanks to > the closure, a routine can be passed as argument to methods which > reply, and then call the routine which will access to the exposed > variable of the closure). Wow, that sounds very interesting! It would be really great (and functionality wise very helpful!) to add lambda/block and closures to ooRexx! ---rony
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