grouping one-liner

Here's my grouping function.  It's shorter than yours, but I don't
know if it's good Slang. It doesn't do the grouping, just returns the
grouping array, given the array length, len, and the bins per group,
nbins. 

We should probably start tossing our utilities around and collecting
useful ones in a central repository.  Since many of us are gradually
learning Slang, this will also help w/ language features and
progamming styles.



define ngrp(len,nbins)
{
 return ([0:len-1:1]/nbins mod 2) * 2 - 1;
}



    davis> Here is my group_data function.  I have it defined in my
    davis> .isisrc file:

    davis> public define group_data (ds, num)
    davis> {
    davis> variable idx, len;

    davis> rebin_data (ds, 0);                 %  unbin data
   
    davis> (idx,,,) = get_data (ds);
    davis> len = length (idx);

    davis> idx = Int_Type [len];

    davis> variable i, s;

    davis> s = 1;
    davis> _for (0, len-1, 1)
    davis> {
    davis> i = ();
    davis> !if (i mod num)
    davis> s = -s;
   
    davis> idx[i] = s;
    davis> }

    davis> rebin_data (ds, idx);
    davis> }



-- Dave