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Re: prograMing: split a list

  • To: mathgroup at
  • Subject: [mg8958] Re: prograMing: split a list
  • From: Leszek Sczaniecki <lsczan at>
  • Date: Mon, 6 Oct 1997 01:59:26 -0400
  • Organization: Concentric Internet Services
  • Sender: owner-wri-mathgroup at

Leszek Sczaniecki wrote:

> What about this solution?
> In[1]:= myList=Table[Random[Integer,{1,200}],{10000}];
> In[2]:= fQ=OddQ;
> In[3]:= {Select[myList, fQ], Select[myList,!fQ]} ;// Timing
> Out[3]= {0.15 Second,Null}


Here is an appendix to my last posting. Michael Trott just reminded me that this
will not work for completely general, user defined boolean function fQ. In that
case you need to do something like that

    {Select[myList, fQ], Select[myList,!fQ[#]&]}

or, if you care about the symmetry of the last expression, define two tests fQ and

    fQ := (# < 100)&
    notfQ := (# >= 100)&     (or not fQ := !fQ[#]&)

   {Select[myList, fQ], Select[myList,notfQ]}


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