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How to flatten a disembodied property list (DPL)?

Sheppie

Hi,

I have a disembodied property list (DPL) which looks like this:

test = list(nil 'a '(1 2 3) 'b nil 'c '( nil 'd '(7 8 9) 'e '(10 11 12) ) 'f '( nil ) 'g '(13 14 15) )

test
(nil a (1 2 3) b nil
c (nil 'd '
    (7 8 9) 'e '
    (10 11 12)
) f (nil) g
(13 14 15)
)

So, every value of the symbol-value pair is either a list (see 'a or 'd or 'e or 'g), an other DPL (see 'c) an empty DPL (see 'f) or nil (see 'b).

After flattening, test should look like:

test
(1 2 3 7 8
    9 10 11 12 13
    14 15
)

So, the DPL has many "hierarchical levels", which all should collapse into one long list. Where an empty DPL and nil should not be included.
The problem I'm having is that I'm having difficulties finding the lowest point, and traversing back.
Or should I just create a procedure that starts at the top and calls itself when it encounters an other DPL?

Any suggestion is appreciated.

Thank you in advance.

With kind regards,

Sjoerd

Parents

  • Sjoerd,

    I assume your list is really like this:

    test = list(nil 'a '(1 2 3) 'b nil 'c '( nil d (7 8 9) e (10 11 12) ) 'f '( nil ) 'g '(13 14 15) )

    rather than

    test = list(nil 'a '(1 2 3) 'b nil 'c '( nil 'd '(7 8 9) 'e '(10 11 12) ) 'f '( nil ) 'g '(13 14 15) )

    (otherwise it has quotes embedded within the quoted lists, which wouldn't make sense). Once you quote the outer list, everything within it is quoted.

    This recursive (non-destructive) function does (I think) what you want. It seems a rather unusual requirement...

    procedure(CCFflattenStrangeDPL(dpl)
  let((key value result)
    dpl=cdr(dpl)
    while(dpl
      key=car(dpl)
      value=cadr(dpl)
      dpl=cddr(dpl)
      result=lconc(result
        copy(
          if(listp(value) && !car(value) then
            CCFflattenStrangeDPL(value)
          else
            value
          )
        )
      )
    )
    car(result)
  )
)

    Andrew

  • in reply to Andrew Beckett

    Andrew responded as I was coding up a solution, but figured I would post mine as well. Also, please refer to Andrew's post on fixing your DPL structure:

    procedure(flatten(data)
  cond(
    (dplp(data)
      foreach(mapcan key reverse(data->?)
        let((val)
          val = get(data key)
          if(listp(val)
            flatten(copy(val)) ; then
            ncons(val)
          )
        )
      )
    )
    (listp(data)
      foreach(mapcan val data
        if(listp(val)
          flatten(copy(val)) ; then
          ncons(val)
        )
      )
    )
    (t
      error("Unexpected value: %L\n" data)
    )
  )
)
test = '(nil a (1 2 3) b nil c (nil d (7 8 9) e (10 11 12)) f (nil) g (13 14 15))
flatten(test) == '(1 2 3 7 8
    9 10 11 12 13
    14 15
)
  • in reply to AaronSymko

    Hi AAronSymko,

    Thank you very much foryour solution and time. Please see my response to Andrews solution as well.

    With kind regards,

    Sjoerd

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