Do you think it would be possible to implement a "finally" construct for native libraries? Basically, what I'm asking for is the ability to register a callback with a specific stack frame that is called when that frame is unrolled.
Regards, Elias On 14 Apr 2016 01:51, "Juergen Sauermann" <juergen.sauerm...@t-online.de> wrote: > Hi Kacper et al, > > I understand. But I would say that using *⎕EA* as you describe is exactly > how > cleanup should be done. I see *⎕EA *not like (as the name may suggest) a > means of > trying different paths until one succeeds like in: > > *'try_A' ⎕EA 'try_B' ⎕EA '**try**_C'** ...* > > but rather as: > > *'cleanup_failed_B' ⎕EA '**try_B'* > > I also don;t see a good way of introducing a defer function without > introducing > a dubious APL syntax extension that would be difficult to read for people > not > knowing the extended syntax. For the sake of compatibility, such things > should, > IMHO, be avoided. > > /// Jürgen > > > On 04/12/2016 02:10 AM, Kacper Gutowski wrote: > > If I understand correctly, Elias wants to have something that would > ensure that every file opened is eventually closed (only more general so > it can be applied to any external resources not only files). That is in > a code similar to the following, to ensure the line 3 is always run even > if there's an error in FUN. > > [1] FD←⎕FIO[3]STH > [2] FUN FD > [3] ⎕FIO[4]FD > > This can be ensured by wrapping FUN call with ⎕EA or ⎕EC. They return > to the caller instead of suspending execution if error happens and this > is correct and expected behaviour. But the intention is to have the > file closed, not making the function unsuspendable, so this would be > a side effect of the solution of using ⎕EA rather than the intended > behaviour. But this doesn't mean there's anything wrong with ⎕EA or > ⎕EC, of course. > > My understanding is that requested is some way to associate some kind of > clean up code with )SI entry that would be run upon that entry being > cleared from )SI regardless of how that happens. > > The way I imagine it, it could look like this (using an imaginary > function ‘defer’ with a name borrowed from Golang; not an actual > transcript): > > ∇ FOO > [1] FD←⎕FIO[3]STH > [2] defer '⎕FIO[4]FD' > [3] FUN FD > [4] other stuff ∇ > > STH←'filename' > ⎕FX 'FUN F' '1+' > > FOO > SYNTAX ERROR > FUN[1] 1+ > ^^ > ⍝ here situation can be examined > )VARS > F FD > )SIS > FUN[1] 1+ > ^^ > FOO[3] FUN FD > ^ > ⋆ FOO > ^ > → > ⍝ here ⎕FIO[4]FD is executed > > -k > > > >
