Re: (rank)
Hi Alex,
Ah. That's what I missed the sort direction of the second argument..
Thank you
Lindsay
On Tue, May 23, 2017 at 10:47 PM, Alexander Burger <a...@software-lab.de>
wrote:
> Hi Lindsay,
>
> > My sample code ("ABRA..) is wrong. Sorry about that.
>
> Ah, I see. No problem.
>
>
> > : (rank 'c '((a . a) (b . b) (d . d)) T) # ???
> > -> NIL
> > : (rank 'd '((a . a) (b . b) (d . d)) T) # ???
> > -> NIL
> >
> > : (rank 'd '((a . a) (b . b) (d . d)))
> > -> (d . d)
> > : (rank 'c '((a . a) (b . b) (d . d)))
> > -> (b . b)
> >
> > The latter two work as I would expect.
> > I expected the first two to return '(d . d)
>
> The reason here is that 'rank' expects a *sorted* list. It traverses the
> list,
> and stops as soon as it can confirm or refute the desired condition.
>
> With a second argument non-NIL, it tries to "Returns the element from lst
> ...
> with a minimal CAR greater or equal to any". However, already the first
> element
> (a . a) is *less* than 'c' or 'd', hence it returns NIL.
>
> If you reverse the list, it works:
>
>: (rank 'c '((d . d) (b . b) (a . a)) T)
>-> (d . d)
>
>: (rank 'b '((d . d) (b . b) (a . a)) T)
>-> (b . b)
>
> It is the purpose of the second argument to tell 'rank' in which direction
> it
> should expect the list to be sorted.
>
> ♪♫ Alex
>
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>
Re: (rank)
Thanks Alex,
My sample code ("ABRA..) is wrong. Sorry about that.
I simplified too much from some other code I have written that has a lot
of unrelated stuff in it.
However, what about these examples? Similar to those of the documentation:
: (rank 'c '((a . a) (b . b) (d . d)) T) # ???
-> NIL
: (rank 'd '((a . a) (b . b) (d . d)) T) # ???
-> NIL
: (rank 'd '((a . a) (b . b) (d . d)))
-> (d . d)
: (rank 'c '((a . a) (b . b) (d . d)))
-> (b . b)
The latter two work as I would expect.
I expected the first two to return '(d . d)
/Lindsay
On Tue, May 23, 2017 at 12:32 PM, Alexander Burger <a...@software-lab.de>
wrote:
> Hi Lindsay,
>
> > : (nil (setq *BitsSA (sort (make (map link (chop "ABRAABRACADABRA"))
>
> *BitsSA is a list of lists of characters:
>
>: (more *BitsSA)
>("A")
>("A" "A" "B" "R" "A" "C" "A" "D" "A" "B" "R" "A")
>("A" "B" "R" "A")
>("A" "B" "R" "A" "A" "B" "R" "A" "C" "A" "D" "A" "B" "R" "A")
>...
>
> > : (rank (chop "BR") *BitsSA)
> > -> ("R" "A" "C" "A" "D" "A" "B" "R" "A")
>
> This does not make sense. You search the ranking list with a *list*
> argument
> (chop "BR"), i.e. ("B" "R")
>
> Same here:
>
> > : (rank (chop "BRA") *BitsSA T)# ???
> > -> NIL
>
> So you compare the CARs of *BitsSA - which are characters (i.e. symbols) -
> with
> lists. A list, however, is always greater than a symbol.
>
> >From https://software-lab.de/doc/ref.html#cmp:
>
>For differing types, the following rule applies: Numbers are less than
>symbols, and symbols are less than lists.
>
> ♪♫ Alex
>
> --
> UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe
>
Re: (rank)
Hi Lindsay,
> : (nil (setq *BitsSA (sort (make (map link (chop "ABRAABRACADABRA"))
*BitsSA is a list of lists of characters:
: (more *BitsSA)
("A")
("A" "A" "B" "R" "A" "C" "A" "D" "A" "B" "R" "A")
("A" "B" "R" "A")
("A" "B" "R" "A" "A" "B" "R" "A" "C" "A" "D" "A" "B" "R" "A")
...
> : (rank (chop "BR") *BitsSA)
> -> ("R" "A" "C" "A" "D" "A" "B" "R" "A")
This does not make sense. You search the ranking list with a *list* argument
(chop "BR"), i.e. ("B" "R")
Same here:
> : (rank (chop "BRA") *BitsSA T)# ???
> -> NIL
So you compare the CARs of *BitsSA - which are characters (i.e. symbols) - with
lists. A list, however, is always greater than a symbol.
>From https://software-lab.de/doc/ref.html#cmp:
For differing types, the following rule applies: Numbers are less than
symbols, and symbols are less than lists.
♪♫ Alex
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