Semantic clash with Base.insert!

[c42f]

insert!(dict, k, val) with a dictionary means something very different from insert! with a Vector. The Vector API from Base is more or less sequence- or iterable-like: insert something at a given index of the sequence, and move the remaining values to make room, preserving iteration order.

I wondered whether this is an oversight, or whether there's a plan to deal with this in some way?

[tkf]

How about push!(dict, k => v)? It works with AbstractDict and AbstractSet:

julia> push!(Dict(), :a => 1)
Dict{Any,Any} with 1 entry:
  :a => 1

julia> push!(IdDict(), :a => 1)
IdDict{Any,Any} with 1 entry:
  :a => 1

julia> push!(Set(), :a)
Set{Any} with 1 element:
  :a

julia> push!(Base.IdSet(), :a)
Base.IdSet{Any} with 1 element:
  :a

[c42f]

push! seems approximately right. Does it matter that AbstractDictionary is not really a container of pairs though? This may lead to oddities, such as after push!(d, e), collect(d) will not contain e?

[tkf]

This may lead to oddities, such as after push!(d, e), collect(d) will not contain e?

Ah, very good point. Actually, insert! looks kind of appropriate now (at least within the functions defined in Base) for me.

insert something at a given index of the sequence, and move the remaining values to make room, preserving iteration order.

I think insert!(::AbstractDictionary, i, v) does the first point right. I don't think the last point is really necessary as iteration order is (usually) arbitrary for dictionaries. The second point ("move the remaining values") is unfortunate but maybe it can be compared to the case where you don't need to "make room"?

julia> insert!([:a, :b, :c], 4, :d)
4-element Array{Symbol,1}:
 :a
 :b
 :c
 :d

[tkf]

Reading JuliaLang/julia#35513 and JuliaLang/julia#36070, I wonder if vectors should implement insertat! and let AbstractDictionary and AbstractDict define insert!. (With the compatibility fallback for insert!(vector, ...), of course.)

[c42f]

Good point. The semantic mismatch between Base insert! and delete! seems very unfortunate.

[andyferris]

My thinking here is that Vector should use insertat!

[c42f]

Agreed. Inserting-into-a-sequence and implicitly shifting the keys (indices) of the rest of the sequence seems like a fairly specialized operation. Not something that many kinds of collection will want to implement, so having a specific rather than generic name for it would be an improvement.