That's disturbing. Oh well, I'll stand by my other assertion - that if you don't know whether the name exists you should assign it before erasing it.
As for the return - it tells you whether the erase succeeded. An erase of a name which does not exist is a success, correct? I mean, the name is not there after it's erased. On the other hand, you could argue that most return values are useless. After all, you can't eat them, even with lots of ketchup. Seriously, though, what application needs to find out whether or not a name was erased? I'm still trying to wrap my head around the idea of that being used for anything practical. Thanks, -- Raul On Wed, Sep 17, 2014 at 3:17 PM, Don Guinn <[email protected]> wrote: > I tried erasing 'list_base_' and list disappeared from z. Also, why bother > with a pretty much useless return? > On Sep 17, 2014 12:55 PM, "Raul Miller" <[email protected]> wrote: > >> That's easy to avoid the problem with erasing names in the path. >> >> Option 1: assign the name using =. before erasing it. >> >> Option 2: use a form of the name which specifies the locale. >> >> Put differently, how is it useful for erase to tell you you have made >> a mistake when what you really want is to not make the mistake in the >> first place? >> >> Thanks, >> >> -- >> Raul >> >> On Wed, Sep 17, 2014 at 2:13 PM, Don Guinn <[email protected]> wrote: >> > It has always bothered me that erase will erase names in the path if the >> > name does not exist in the current locale. It kind of makes sense to do >> > that, but erasing names from other locales, particularly the z locale >> does >> > not seem right either. I created my own erase to only erase from the >> > current locale but it is not pretty and seems inefficient if used a lot. >> > Perhaps adding a dyadic option to 4!:55, values 0 and 1. Zero being the >> > current way to erase from the path and the default, and 1 restricting >> erase >> > to the current locale. >> > >> > The problem with avoiding local names is easily avoidable by creating >> > another erase verb which is explicit instead of tacit. But if erase is >> made >> > dyadic then maybe 2 could mean only erase local names or 3 for only >> global >> > names. >> > >> > Then there is the problem of erasing a pendent name. This results in a >> > stack error. Why not make erase return 1 if successful and 0 if not as >> > Linda expected instead of if the name is legal or not? That makes the >> > return more useful. >> > >> > On Wed, Sep 17, 2014 at 11:42 AM, Raul Miller <[email protected]> >> wrote: >> > >> >> The result from erase is telling you that the name is legal to erase. >> >> To get a zero, try erase 'i.' >> >> >> >> If you want to see whether the operation succeeded, you'll need to do >> more >> >> work. >> >> >> >> One issue you need to consider is the class of the name. >> >> >> >> nameClass=: [: nameclass ;: ::] >> >> >> >> Only names with a non-negative class can be removed by erase. >> >> >> >> Another issue which might interest you is whether the name is defined >> >> locally. This needs work (it gives undefined names a definition), but >> >> is a hint as to how you could test for whether the name is defined >> >> locally: >> >> >> >> nameLocal=: [: {.@".@('0[',],'=:',]) ::1:&> ;: ::] >> >> >> >> Another issue which might interest you is what locales the name is >> defined >> >> in. >> >> >> >> nameLocales=:[: 3 :0 S:0 ;: ::] >> >> path=. ~.(,18!:2)18!:5'' >> >> test=.'(p P y)](4!:0<''',y,'__y'')[(''''P y)[p=.(P=.18!:2)y' >> >> <path#~_1<(3 :test)"0 path >> >> ) >> >> >> >> Example use: >> >> nameClass 'this is a test' >> >> nameLocal 'this is a test' >> >> nameLocales 'this is a test' >> >> >> >> nameClass gives you a list of numbers in the range _2 through 3 >> >> indicating whether the name is illegal, undefined, noun, adverb, >> >> conjunction or verb. >> >> >> >> nameLocal gives you a 1 for names with local definitions (and for >> >> illegal names). Be careful, though, because it will define the name if >> >> it's not already defined. >> >> >> >> nameLocale gives you a boxed list of the locales where you can find >> >> the definition of the name. >> >> >> >> Anyways... there's lots of ways things could work. But why would you >> >> erase a name in the first place, if you don't know that it exists? >> >> >> >> Thanks, >> >> >> >> -- >> >> Raul >> >> >> >> >> >> >> >> On Wed, Sep 17, 2014 at 10:40 AM, Linda Alvord <[email protected] >> > >> >> wrote: >> >> > For a long time this has puzzled me. >> >> > >> >> > >> >> > >> >> > A=:2 4$i.8 >> >> > >> >> > erase 'A' >> >> > >> >> > 1 >> >> > >> >> > erase 'A' >> >> > >> >> > 1 >> >> > >> >> > >> >> > >> >> > It seems the second time it tells me it erased A it is lying because >> >> there >> >> > should be no A any longer. >> >> > >> >> > >> >> > >> >> > Now it is really bothering me. >> >> > >> >> > load 'viewmat' >> >> > >> >> > ]GRB=:1 0 2{"1 (#:i.8){0 255 >> >> > >> >> > ]T=:+/~i.16 >> >> > >> >> > GRB viewmat T;'T'GRB viewmat i.16 >> >> > >> >> > >> >> > >> >> > ]C=:i.12 >> >> > >> >> > GRB viewmat C >> >> > >> >> > >> >> > >> >> > ]D=:3 4$i.12 >> >> > >> >> > GRB viewmat D >> >> > >> >> > >> >> > >> >> > ]M=:5 3$i.15 >> >> > >> >> > GRB viewmat M >> >> > >> >> > >> >> > >> >> > GRB viewmat 7 3$i.21 >> >> > >> >> > >> >> > >> >> > ]B=:4 4$i.16 >> >> > >> >> > GRB viewmat B >> >> > >> >> > >> >> > >> >> > GRB viewmat |: B >> >> > >> >> > >> >> > >> >> > GRB viewmat |.|:B >> >> > >> >> > >> >> > >> >> > If I run a different script with images in 1.ijs and then run >> >> 2.ijs I >> >> > get images all mixed up. Even If I remove all png's from the temp >> >> folder, >> >> > ghosts of previous images appear. I turn of JHS.bat and the try >> 2.ijs >> >> > and old images show up. They seem to be coming from the clipboard >> >> possibly. >> >> > Erasing names does not seem to help, but I'd like it better if I only >> >> got a >> >> > 1 when it finds something with the given name and then was not >> willing >> >> to >> >> > erase it abain. >> >> > >> >> > >> >> > >> >> > However, it is great to see any images! Also, jqt seems to be >> >> unphased >> >> > by thses ghosts. >> >> > >> >> > >> >> > >> >> > Linda >> >> > >> >> > >> >> > >> >> > ---------------------------------------------------------------------- >> >> > 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 >> > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
