On Thu, Jun 9, 2022 at 4:07 PM Elijah Stone <elro...@elronnd.net> wrote: > On Thu, 9 Jun 2022, Raul Miller wrote: > > when [local variables] can be accessed, they can be updated. > > Updating locals is a local transformation, not global, in which respect they > can be seen as syntax sugar.
That seems like a moot point, when we can expose our code to global transformations. > > Perhaps this distinction is best illustrated by considering memory mapped > > files -- here, J bends its rules, mapping J values onto OS managed storage. > > ... But what you are observing here is a change in the data pointed to by the > variable, not in the variable itself. I do not understand the distinction you are drawing here: what would "a change in the variable" which is not "a change in the data pointed to by the variable" look like? > (In languages with closures, local variables really are mutable.) I suspect, here, you are trying to say something about scope. > > When things are not working right, how does the developer inspect values > > stored in thread-local names in the suspended thread (or task-local names > > in the suspended task)? > > T.n to thread number n while debugging. Presumably that also gets you access > to n's task-locals. Fair enough. > > That said, I am getting the feeling that we ought to adopt the "use case" > > discipline here. Presumably you have in mind some useful model of how this > > would be used -- coroutines or whatever. And, I think, those sorts of > > examples should be made explicit, so that we can better understand them. > > Sure. I don't have a particular use-case in mind, for myself, at the moment. > But consider jd: it uses global variables to pass around state. And I know > Eric said he wants to parallelise it (at least for queries). Changing those > variables to be thread-local would be a minimally invasive way of enabling > such a change. Stuffing them in locales would also serve that end. -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
