This method has two typicaluse cases. The first case is to convert sublists of a list E to their corresponding indices. For technical reasons, the accepted input is a list L of sublists of E, and the output is a list of sets of indices, one set for each sublist in L. Note that the order of elements in the sublist is lost, when viewed as a set.

The second case is with a matroid as input. Here the ambient list E is taken as the ground set of the matroid (i.e. E = M_*), and L should be a list of elements of M (not a list of lists); in this case the inverse of this method is given by taking subscripts with respect to M.




In this case, if L is not a sublist of M_*, then a warning is printed, and L itself is returned. This is done so that if a user inputs a list of indices, then it will be interpreted as a set of indices. For more on this, cf. groundSet.
The object indicesOf is a method function.