🚀 go-pugleaf

In article <ANDKA.92Nov2103650@aste12.IDA.LiU.SE> andka@IDA.LiU.SE (Andreas Kagedal) writes:

AK> In article <PLUMMER.92Nov1091801@nutmeg.cs.swarthmore.edu> plummer@cs.swarthmore.edu (David Barker-Plummer) writes:

AK> The original poster (Ulrich Mayring) wrote:
UM> > Hello netters, I have a problem:
UM> > 
UM> > I have a list and need to recursively pick two elements out of it. I
UM> > need every pair of elements in every order, however the order of the
UM> > pair itself is not important. It should also be possible to pick an

AK> Now I say:

AK> This will cause every pair to occur twice, since the order of the pair
AK> was not important. A modified version:

Your criticism is completely correct, and your code works, although
the conventional name for your member/3 predicate is select/3.  I
interpreted "every pair of elements in every order" to mean that (a,b)
and (b,a) should both appear, although on closer insepection this
appears to be contradicted by the clause "the order of the pair itself
is not important".  I read this latter as meaning that it didn't
matter what order the pairs were produced.

-- Dave