I love closures! I've only used them hacking about in groovy but they're really nice. What else is on your todo list? Have you given aspects any thought?
Rick McGuire wrote: > I've been giving some thought to whether closures could be added to > the language for some time, but the issues generally lie on the > calling end. That is, what is the syntax to be used that would allow > a closure to be created without cluttering up the language with lots > of special exceptions or awkward syntax. Ideally, a closure would be > something that would just be an extension of normal expression syntax. > Closures would be assignable to variables and, of course. allowed as > method arguments. Implemented that way, there's no additional > overhead needed on the argument calling mechanisms. So far, I've not > found a syntax that I'm happy with. > > There are other side issues that need to be addressed, such as > ensuring that the closure somehow becomes invalid when the environment > where it was created is no longer valid, or the more interesting case > of a closure passed to a method that does an early reply...now the > closure will be executed on an entirely different thread. > > This is an interesting idea, but not one I'm prepared to jump on and > accept until all of the implications are written down and discussed. > Right now, there are lots of more well-defined enhancements on my todo > list. If you'd like to get involved in any of these, just speak up > and I'll suggest a few. > > Rick > > On Tue, Jul 22, 2008 at 5:01 AM, Jean-Louis Faucher <[EMAIL PROTECTED]> wrote: > >> Sorry, my previous mail was sent from a flashmail, was a bad idea ! I hope >> this one will be more readable... >> >> As other users (see comp.lang.rexx/2005-11/msg00065.html), I use sometimes a >> function iif which on the basis of a condition selects between two values : >> iif: >> use strict arg condition, iftrue, iffalse >> if condition then >> interpret "return" iftrue >> else >> interpret "return" iffalse >> >> I see two drawbacks with this function : >> The caller must surround the 2nd and 3rd argument by quotes, to pass a >> string to the function. Example : say iif(s == .nil, 's', 's~id') >> The whole scope of the caller must be visible, to let the evaluation have >> access to all the variables of the caller. So I can't implement this >> function as a procedure or a routine or a method. And I can't put it in my >> library that I requires from my scripts. >> >> I had a look at the function RexxActivation::run (putting a breakpoint here >> is very instructive). >> I see that each instruction is evaluated by : nextInst->execute(this, >> localStack) >> It seems that each instruction is in charge of the evaluation of its >> arguments, using : result = this->expression->evaluate(context, stack) >> >> Could we imagine that such a behavior is possible at the level of user rexx >> code ? The not-evaluated-expression passed to the rexx code should bring the >> context and stack with her, to let the user write >> expression->evaluate() >> >> A not-evaluated-expression is not of type String. Should be of a new type >> (Closure ?) which supports the method evaluate(). >> >> Example : >> >> iif: procedure >> use unevaluated arg condition, iftrue, iffalse >> if condition->evaluate() then >> return iftrue->evaluate() >> else >> return iffalse->evaluate() >> >> Here " unevaluated " is a keyword to indicate the deferred evaluation of the >> arguments. >> I can use a procedure or routine or method since the evaluation of the >> expression is done in the caller's context. >> >> The caller calls the function without surrounding the expressions in quotes >> : >> say iif(s == .nil, s, s~id) >> >> And there is no error like Object "The NIL object" does not understand >> message "ID" when s is nil. >> >> Jean Louis >> >> ------------------------------------------------------------------------- >> This SF.Net email is sponsored by the Moblin Your Move Developer's challenge >> Build the coolest Linux based applications with Moblin SDK & win great >> prizes >> Grand prize is a trip for two to an Open Source event anywhere in the world >> http://moblin-contest.org/redirect.php?banner_id=100&url=/ >> _______________________________________________ >> Oorexx-devel mailing list >> Oorexx-devel@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/oorexx-devel >> >> >> > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Oorexx-devel mailing list > Oorexx-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/oorexx-devel > > ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Oorexx-devel mailing list Oorexx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/oorexx-devel
