keys and getindex of OrderedSet

[huaiyuduan]

My understanding of a set is a collection of keys without values. Therefore, I would expect OrderedSet to have keys as elements and their positions in the set as values or indices. This interpretation agrees with the description of Base.getindex: "Retrieve the value(s) stored at the given key or index within a collection."

The current implementation of getindex(ordered_set, i) returns the ith element in ordered_set which is opposite to this interpretation. I agree that it's useful to get the element at a given position, but it's more intuitive to use ordered_set[i] instead. Similarly, the current implementation of keys(ordered_set) returns 1:length(ordered_set) instead of collect(ordered_set).

[huaiyuduan]

Just realized that Julia actually converts ordered_set[i] to getindex(ordered_set, i). Nevertheless, is there an efficient way to get the index of an element in an OrderedSet?

[StephenVavasis]

Note that OrderSet is part of OrderedCollections, which is not this repository (DataStructures) but is adjacent. So I am closing this issue and requesting that you reopen it in OrderedCollections if you wish.

[timholy]

ordered_set[i] is currently deprecated:

OrderedCollections.jl/src/ordered_set.jl

Lines 84 to 91 in 6497eb5

	# Deprecated functionality, see
	# https://github.com/JuliaCollections/DataStructures.jl/pull/180#issuecomment-400269803
	function getindex(s::OrderedSet, i::Int)
	Base.depwarn("indexing is deprecated for OrderedSet, please rewrite your code to use iteration", :getindex)
	s.dict.ndel > 0 && rehash!(s.dict)
	return s.dict.keys[i]
	end

Personally I think getting rid of it is the right answer, but I know there have been voices to the contrary.