Use BSL with List Abbreviation.
On Mar 3, 2015, at 3:50 PM, Rufus <rlagg...@mail.com> wrote: > Alexander > > Well, in fact, I thought it worked for me, too. And then it stopped > working; DrR threw an "application: not a procedure;" error saying it > was given a null list instead of an application. Removing the parens got > it working again. > > Now that just doesn't make any sense at all but that's what I seem to > have observed. Looking at some StackOverflow responses on similar errors > I found that parens in certain positions are interpreted as invoking a > function regardless of what may in fact be inside the parens. IOW, extra > parens will trigger that error. I believe that initially it was working. > Perhaps I had run it in the executable pane instead of loading and > running the defs file? If I have more time somewhere along, I'll try to > recreate things. > > When I first defined atom? I was using a very small definitions file > with the " #lang racket" spec; IIRC atom? worked. After trying BSL and > then going back to using the #lang spec and adding some comments and the > list of variable defs - it didn't work. > > At the moment I don't have any good ideas, except to chg the code to get > it to work and proceed. > > Rufus > > > > On 03/03/2015 02:21 PM, Alexander D. Knauth wrote: >> This works for me: >> (define atom? (lambda (arg1) >> (and (not (pair? arg1)) >> (not (null? arg1))))) >> >> >> On Mar 3, 2015, at 3:16 PM, Rufus <rlagg...@mail.com> wrote: >> >>> On page 10 of TLS there is a note defining the "atom?" function for the >>> reader to use w/Lisp or Scheme. The definition for Scheme (which is the >>> most likely one to use for DrR) does not work. To fix one must remove >>> the parens that open at the "and". Apparently the DrR >>> compiler/interpreter sees them as an attempt to invoke a function and >>> that's not correct here. I don't know if other Lisp versions would find >>> the code in the book correct. >>> >>> In the text below XXX shows where I removed a set of parens to make the >>> function work. >>> >>> (define atom? (lambda (arg1) >>> XXX and (not (pair? arg1)) >>> (not (null? arg1)) >>> XXX >>> ) >>> ) >>> >>> >>> Rufus >>> ____________________ >>> Racket Users list: >>> http://lists.racket-lang.org/users >> > ____________________ > Racket Users list: > http://lists.racket-lang.org/users ____________________ Racket Users list: http://lists.racket-lang.org/users
