Atom - Ġ - Group Indices by Value

Characters: Ġ

Tags: array

Arity: monadic

This atom is monadic, which means it takes one argument.


Group the indices of a list by the corresponding values.


This returns a list of lists. Each number in [1, 2, ..., len(z)] will appear exactly once. Each sub-list will contain indices that map to the same value; that is, i and j are in the same sublist if and only if z[i] == z[j]. The sublists are ordered by the element they correspond to.