On 4 Aug 2011, at 10:36, Lyndon Maydwell wrote: > nub Heh, our differing answers point out an ambiguity in the question. Luca, given [5,10,10,5] what is this function expected to produce? if you want [5,10] then nub is correct. if you want [5,10,5] then map head . group is correct. Bob