Oh... well... I guess I disagree with the model you posted here, about how to implement the peg game: I think that a spec requiring five arrays is unnecessarily redundant.
That said, I did make an error in one of my posts, which I am only just now realizing: the move_table depends on the size of the board, and I didn't deal with that in my supposed general case implementation. Fortunately, the fix is straightforward, and I could post that if you wanted. Anyways... to address the complexity argument you're raising, you can have up to four hetrogenous unboxed array parameters in a recursive context in J without resorting to objects to represent them. Specifically: verbs can take one or two arguments, adverbs give you an additional argument and conjunctions another on top of that. With objects, or with boxing, you can go much higher - but that can indeed feel kludgy if you need an object or box for every recursive invocation. But you can also often rearrange things to not need so many recursive parameters. And for the peg problem, I only see three significant arrays: the board, the moves to reach that board and the list of legal moves. Recursive contexts give you a stack, allowing you to backtrack with these arrays. I'm not seeing why you need more than that? Thanks, -- Raul On Wed, Jun 7, 2017 at 2:26 PM, Michael Rice <[email protected]> wrote: > Thanks for the paste tip. I was unaware of that feature. > > I'm "giving up on" the peg game. I didn't think that needed identifying as > it's been my only focus. I think of "academic exercises" as homework, > seeking answers to which is, rightly, taboo on computer language web-sites. > > The peg game search function has five arrays it recursively manipulates to > a solution, three of which begin as empty, all having varying shapes, even > empty, as they pass through recursions. From what I've read in *Learning J*, > for their heterogeneous shapes they would have to be boxed to be passed as > a functional parameter, un-boxed inside a recursive pass to be altered, and > then boxed again to be passed on to the next recursion. I didn't say it was > impossible, just that it seemed kludgy, or, as you put it "forced." > > I spent quite a bit of time with Haskell. As a functional language it's > hard to beat, but some problems on which I used it I felt like I was having > to go around the block just to get next door. Why bother? > > Thanks for your input. > > > On Wed, Jun 7, 2017 at 1:11 PM, Raul Miller <[email protected]> wrote: > >> When pasting into gmail, please use "Paste and match style" to avoid >> the extra blank lines that someone at google somehow managed to work >> into the default Paste action. >> >> That said: >> >> my_empty =: }. 1 >> < my_empty >> ┌┐ >> ││ >> └┘ >> >> What you are seeing here is not an empty list of boxes but a box >> containing an empty. Or, ok, yes: "an empty box". >> >> Note also that a: is the same: >> >> a: >> ┌┐ >> ││ >> └┘ >> a: -: <}.1 >> 1 >> >> (Finally, I should perhaps note that I have no idea what problem you >> are giving up on. Usually, though, "academic exercises" - which >> typically focus more on how the goal is reached than on reaching the >> goal - tend to feel forced in J.) >> >> Thanks, >> >> -- >> Raul >> >> >> On Wed, Jun 7, 2017 at 1:03 PM, Michael Rice <[email protected]> wrote: >> > @robert therriault >> > >> > my_empty =: }. 1 >> > >> > my_empty >> > >> > >> > f my_empty >> > >> > 1 >> > >> > < my_empty >> > >> > ┌┐ >> > >> > ││ >> > >> > └┘ >> > >> > >> > An empty box? >> > >> > >> > I'm beginning to see the problem I was thinking of doing in J is >> ill-suited >> > to the language. It could be done, as it could in any computer language, >> > but the solution would be pretty kludgy. >> > >> > >> > I'll soon think of something else on which to apply J. It's already >> > invading my sleep. Going through exercises is no way to get into a >> > language. One needs a problem on which to focus it. I've been wanting to >> > explore cryptography more deeply, and J seems ideal for it. >> > >> > >> > Thanks to all, >> > >> > >> > Michael >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > >> > On Wed, Jun 7, 2017 at 12:01 PM, robert therriault < >> [email protected]> >> > wrote: >> > >> >> I'm going to look at these results through the lens of Shape ($) >> >> >> >> f =: (1&,) >> >> f 2 >> >> 1 2 >> >> $ f 2 NB. shape is 2 >> >> 2 >> >> f '' >> >> 1 >> >> $ f '' NB. shape is 1 >> >> 1 >> >> empty NB. it is a verb in my environment >> >> (i.0 0)"_ >> >> f empty >> >> f empty NB. result of two verbs and no arguments is just the two verbs >> >> f empty 2 NB. this is where you expect to have a 1 returned >> >> >> >> $ f empty 2 NB. shape is 1 0 >> >> 1 0 NB. one line of no items means no display >> >> >> >> I think it is the second dimension of EMPTY as opposed to NULL that is >> >> tripping you up. >> >> >> >> NULL=.'' >> >> $ NULL >> >> 0 >> >> EMPTY >> >> $EMPTY >> >> 0 0 >> >> EMPTY-:empty 1 >> >> 1 >> >> >> >> In answer to your most recent question Michael, I would say just make >> sure >> >> that the empty list that you pass is the right shape. >> >> >> >> Cheers, bob >> >> >> >> > On Jun 7, 2017, at 8:48 AM, Raul Miller <[email protected]> >> wrote: >> >> > >> >> > empty is a verb >> >> > f is a verb >> >> > >> >> > so f empty is a verb (a hook) >> >> > >> >> > f=: 1&, >> >> > (f empty) 3 >> >> > >> >> > >> >> > >> >> > $(f empty) 3 >> >> > 3 0 >> >> > $(f empty) 5 >> >> > 5 0 >> >> > >> >> > The reasons for this are documented at >> >> > http://www.jsoftware.com/help/dictionary/dictf.htm (hooks) and >> >> > http://www.jsoftware.com/help/dictionary/d630n.htm (x m&v y). >> >> > >> >> > That said, verbs take arguments and empty is a verb - it always >> >> > produces an empty result, but only when it gets an argument. >> >> > >> >> > I hope this helps, >> >> > >> >> > -- >> >> > Raul >> >> > >> >> > >> >> > On Wed, Jun 7, 2017 at 11:39 AM, Michael Rice <[email protected]> >> >> wrote: >> >> >> Oops! Guess I creamed empty. Will close and regen Jqt before >> proceeding. >> >> >> >> >> >> Done! >> >> >> >> >> >> f =: (1&,) >> >> >> f 2 >> >> >> 1 2 >> >> >> f empty >> >> >> f empty >> >> >> >> >> >> Shouldn't it have returned >> >> >> >> >> >> 1 >> >> >> >> >> >> ? >> >> >> >> >> >> On Wed, Jun 7, 2017 at 11:22 AM, robert therriault < >> >> [email protected]> >> >> >> wrote: >> >> >> >> >> >>> One thing to remember is that empty is already defined as a verb >> >> >>> >> >> >>> empty >> >> >>> (i.0 0)"_ >> >> >>> >> >> >>> So if you overwrite this you may break some code if you have >> previously >> >> >>> relied on the existing verb definition. >> >> >>> >> >> >>> I think along the lines that Pascal mentioned that null could be >> >> similarly >> >> >>> defined as >> >> >>> >> >> >>> null NB. check that it is not already used >> >> >>> |value error: null >> >> >>> null=:(i.0)"_ >> >> >>> NULL NB. check that it is not already used - uppercase for global >> >> >>> nouns is a convention I like and is often seen in J code >> >> >>> |value error: NULL >> >> >>> NULL=:'' NB. I use this as the null string (same as what John >> >> suggested) >> >> >>> NULL-:null 2 NB. any argument produces NULL from null >> >> >>> 1 >> >> >>> >> >> >>> Hope this helps, >> >> >>> >> >> >>> Cheers, bob >> >> >>> >> >> >>>> On Jun 7, 2017, at 8:09 AM, 'Jon Hough' via Programming < >> >> >>> [email protected]> wrote: >> >> >>>> >> >> >>>> >> >> >>>> I may be wrong in doing this, but I usually write >> >> >>>> empty=: '' >> >> >>>> to signify an empty list, array, matrix etc. >> >> >>>> >> >> >>>> >> >> >>>> On Jun 7, 2017, 23:59, at 23:59, Michael Rice <[email protected] >> > >> >> >>> wrote: >> >> >>>>> Is there a special "noun" for an empty list? >> >> >>>>> >> >> >>>>> Creating one seems enigmatic. >> >> >>>>> >> >> >>>>> empty =: 1 2 >> >> >>>>> empty >> >> >>>>> 1 2 >> >> >>>>> empty =: }. empty >> >> >>>>> empty >> >> >>>>> 2 >> >> >>>>> empty =: }. empty >> >> >>>>> empty >> >> >>>>> >> >> >>>>> empty1 =: >> >> >>>>> |syntax error >> >> >>>>> | empty1=: >> >> >>>>> ------------------------------------------------------------ >> >> ---------- >> >> >>>>> 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 >> >> >> > ---------------------------------------------------------------------- >> > 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
