A visually useful adverb helps here: sfX =: 1 : '][u'
ipm sfX ip 0 1 2 this works with deterministic method: (rhs executed first) (ipm ] 3 : 'y~' ) 'ip' 0 1 2 (3 : 'y~' [ ipm ) 'ip' 2 1 2 ( 3 : '(y) =: 2(0}) y~' ] 3 : 'y~' ) 'ip' 0 1 2 (3 : 'y~' [ 3 : '(y) =: 2(0}) y~' ) 'ip' 2 1 2 Its conceivable to want the behaviour, and its easy to avoid. In terms of philosophy, I have called bonded dyads dyadically by error more often than intentionally, often resulting in lockup. But its a cool feature I have also used intentionally. Removing it will not be considered. I think the above has probably had intentional use in the wild, and is easily bypassed to get the "sane result". Its also easy to deterministically use the modified "side effect" value by composing on the function. I also can't mess up this expression (3 : 'flag =: 1' a:) 3:`[@.] flag =:0 3 The argument for changing it depends on: You could never intentionally want to have a "primarily" side effect function conditionally "improve" an argument depending on whether it references it. ----- Original Message ----- From: Henry Rich <henryhr...@gmail.com> To: sou...@jsoftware.com Sent: Tuesday, June 21, 2016 10:16 AM Subject: Re: [Jsource] Language committee: in-place assignment rules The fix would be to suppress in-place assignment if the name is on the stack in a higher-level sentence, and would not affect anything that doesn't use in-place assignment. Henry On 6/21/2016 1:32 AM, 'Pascal Jasmin' via Source wrote: > At first I thought this was 3. normal behaviour > > the assignment to ip is independent of the return value (which happens to be > ip) or the argument value. > > > The issue here though is that (ipm'') gets evaluated prior to ip, which is > surprising. also happens with: > > ((ipm '') ] ]) ip > 2 1 2 > > but good news: > > ip =: i. 3 > (] [ ipm ) ip > 0 1 2 > ip > 2 1 2 > (ipm ] ]) ip > > 0 1 2 > > also behaves normally. while these don't. > > > (ipm ] ip"_ ) '' > 2 1 2 > (ip [ ipm ) '' > 2 1 2 > > The workaround to get either behaviour is easy. In my first example I think > the parentheses gets executed before the right tine. > > fixing it could be dangerous... could mess with: > > inl=:(cocurrent@] ".@] [)"1 0 > > ----- Original Message ----- > From: Henry Rich <henryhr...@gmail.com> > To: Source forum <sou...@jsoftware.com> > Sent: Monday, June 20, 2016 10:45 PM > Subject: [Jsource] Language committee: in-place assignment rules > > The issue: > > ipm =: 3 : 0 > > ip =: 2 (0}) ip > > ) > > ip =: i. 3 > > (ipm '') ] ip > > 2 1 2 > > > As you see, ip was modified by call to ipm, which did an in-place > assignment. This violates the rules, which say that the value of ip > should have been stacked. In fact, a pointer to the value is stacked. > > > This requires a decision. I think we need a committee of J Language > Experts to decide how to resolve issues like this, and future enhancements. > > > The choices as I see them are: > > 1 - Fix to conform to the Dictionary. Possible; would slow things down > a little; would make some assignments currently done in-place perform a > copy. > > > 2 - Ignore it. Leave as is. > > > 3 - Embrace it - declare that in-place assignments to global variables > may affect previously-stacked references to the same name. [With local > variables the problem does not arise] > > Now we need a Language Committee, and a decision. > > > Henry > > > > > > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
