/ Published in: Scheme
Given an an associative list ((k1 . v1) (k2 . v2) ... (kn . vn)), with possibly equal values for ki, it returns another alist where all cells have distinct keys and where values originally associated to the same key have been grouped as a list in the new cons cell. Ouch! This is much harder to explain than to code. Just check the commented example in the code.