Rony, this was added to NetRexx back in the 1990s. ooRexx does it differently, for whatever reason. Whatever the case, it is always better to 'spell out' the short-circuits in the code rather than rely on weird notations, surely? That way, people who read the code later can see exactly what the programmer intended, rather than having to infer it from some piece of code and notation that quite possibly was wrongly coded in the first place. Very few C coders understand the difference between '&' and '&&', for example. They randomly use both until the compiler complains. In short: if the programmer wanted to 'save time' with a short-circuit then it would be better if they learned to make their code simpler and more readable. If they wanted to do a second test only if the first succeeded, they can always write that explicitly. And anyone who later reads that code will thank them for it. That's why Rexx was designed to be (and hopefully still is): a language that is understandable -- and, more importunately, usable -- to most people. Mike
_____ From: Rony G. Flatscher [mailto:rony.flatsc...@wu.ac.at] Sent: 05 September 2020 19:30 To: oorexx-devel@lists.sourceforge.net Subject: Re: [Oorexx-devel] Short cutting logical operators On 04.09.2020 15:51, Mike Cowlishaw wrote: I think you all know my opinion on weird notations in languages that are only known and used by a few 'elite' programmers -- yet are all-too-easily misunderstood by less-practiced (or simply less-able or infrequent) programmers... Yes, I think everyone concurs. However, the question still remains, if one wishes to add the ability to short-circuit to Rexx (like programmers coming from C/++/#, Java etc are accustomed to and surprised that this concept is not available in Rexx), how to do it. Currently Rick added the comma as a delimiter indicating a short-circuit using and concatenations. Then, if short-circuiting or concatenations should be supported, how to allow them to be expressed in a "Rexxish" manner that is not only known to a few 'elite' programmers, but anyone who comes from C/++/# or Java? ---rony _____ From: Erich Steinböck [mailto:erich.steinbo...@gmail.com] Sent: 04 September 2020 14:22 To: Open Object Rexx Developer Mailing List Subject: Re: [Oorexx-devel] Short cutting logical operators You're right. I've often wondered whether a method call really *must* evaluate all its arguments upfront. What about lazy evaluation? Only evaluate an argument when it is actually required, i. e. accessed for the first time? On Fri, Sep 4, 2020 at 3:17 PM Rick McGuire <object.r...@gmail.com> wrote: Hmmm, I found an awkward bit with this proposal. For the operators, these are all transformed into method calls under the cover, so "a | b" gets executed as "a~'|'(b)", where the object on the left hand side does the evaluation of the condition. This allows any class to override the '|' and '&'. With the overrides, the evaluation needs to be handled directly by the operator code because there's no way to delay evaluation of a method argument, and it would be very difficult to allow something like that to exist. I'm not sure I'm comfortable with '*|' and '*&' be special cases as operators. Rick On Fri, Sep 4, 2020 at 9:03 AM Rick McGuire <object.r...@gmail.com> wrote: There's been a bit of a discussion about the short-cutting conditional lists implemented by IF, WHEN, et al. I find that construct very useful, but as the discussion on the list has revealed, it has its limitations. It would actually be fairly trivial to implement AND and OR operators that can do short-cut evaluation. Of course, this is not possible for XOR, which always requires both values. The real questions are 1) should it be done and 2) what should the operator be. I've been tentatively using *& and *| in my thinking about this, but there are certainly other possibilities. Rick
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