Re: A nil puzzle

[Stephen C. Gilardi]

There was a recent suggestion here:

        http://groups.google.com/group/clojure/msg/32d323e15f8ce624

about the proper value of:

        (clojure.contrib.lazy-seqs/combinations)





        (clojure.contrib.lazy-seqs/combinations) return ([])

or are they in conflict or unrelated?

--Steve

On Jan 23, 2009, at 7:20 AM, lpetit wrote:

(and perhaps by extension (clojure.contrib.lazy-seqs/combinations '()) (or any number of empty seq arguments)) Does a decision to use empty collections in the powerset case fit well with the suggestion that

+1.

#{} is the empty set, () is the empty list, {} is the empty map.

Cheers,

--
Laurent

On 23 jan, 10:17, Konrad Hinsen <konrad.hin...@laposte.net> wrote:

On 23.01.2009, at 09:35, Mark Engelberg wrote:

Now, here's the puzzle. Let's say you want to convert this idea over

to working with lists, or perhaps sequences in general.

Should (powerset '(1 2 3)) print as:
(() (1) (2) (3) (1 2) (1 3) (2 3) (1 2 3))
or
(nil (1) (2) (3) (1 2) (1 3) (2 3) (1 2 3))

My vote is for (), because it specifically represents the empty
subset of a list, rather than a generic "nothing in here" value,
which is my interpretation of nil.

between lists and sequences and the role of nil and the empty list, so

I look forward to hearing the responses.  Let the debating begin!

This reminds me of the long debates in the APL community about the
shapes of empty nested arrays :-)

Konrad.

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