GDL> test=interpol([1,2], [2, 1], 2)
1 2 0
% FINDEX: binary search failed
% Error occurred at: FINDEX 89 /cm/shared/apps/gdl/0.9.4/share/gnudatalanguage/lib/findex.pro
% INTERPOL 102 /cm/shared/apps/gdl/0.9.4/share/gnudatalanguage/lib/interpol.pro
Perhaps the discussion here might be somehow relevant:
Thanks for the reply but I don't believe it's the same issue (I already found that report when searching for this problem).
I think that problem relates to "x must be strictly increasing or decreasing in the 3-parameter case" and not capturing the cases where it isn't. That's clearly not the issue here.
patch for the findex bug was available on the web. fixed.