Why do Elixir maps have an update syntax but no insert syntax, meanwhile Erlang has both?

I don’t know, but how do you think this should look in Elixir?

Map#{a := update, b => new}

I frequently struggle to remember when to use which operator in the Erlang syntax. So my goal was to introduce syntax for the struct-like API (i.e. you expect the keys exist and you can only update them) and leave the dictionary-like API (adding and removing keys) in the Map module. So you can do Map.put/3 to add, Map.delete/2 and so on.

If we are in topic was there a discussion to allow insert of map keys within update struct syntax? That may be a good resource to read …

If there was, it was a long time ago, before 1.0, on the elixir-lang-core mailing list.

I honestly can’t tell you, although I also don’t think it’s relevant here. Half of that is already implemented in Elixir today, namely Map#{a := update} as %{map | a => :update}, so I don’t see that as being the blocker. I’m just trying to understand why something analogous to Map#{ b => new} doesn’t exist in Elixir.

But there isn’t anything specific about the update syntax which makes it exclusively for structs since you’re able to update maps whose keys are of any type.

Yes, exactly. Which is why I said “struct-like” but indeed, it works for regular maps too.

So I guess I still don’t understand why that syntax isn’t included. It sounds like you’re saying the reason for Elixir not having the map literal insert syntax is because your thought was that insertions are more aligned with dictionary operations and thus should only be done through the Map module. Yet the update syntax is allowed, which is counterintuitive to me because I would think if one is supported then the other should be as well due to the close relationship between the two operations, no? Otherwise, why not restrict its use to only structs where insertions are invalid?

An Elixir struct is a map with a known set of atom keys. For a struct, an insert would not make much sense, but updates are very common. I don’t know about others, but I only use the shorthand update syntax for structs, ie: %{struct | field: value}, For plain maps, I always use the Map.put/3,

Elixir uses : for atom keys for developer ergonomics.If Elixir need to support both insert and update in shorthand syntax, there will be 2*2=4 different notations, which would be hard to remember.

If you attempt to update a field which doesn’t exist in a struct using the update syntax, an exception will be thrown. I don’t see why that logic couldn’t be extended when attempting to insert a key into a struct if the syntax were supported.
Whether it is a struct or map, I always prefer the update syntax if I know the key must exist. I want to know if the state is contrary to what I expect and Map.put doesn’t allow for that. I believe that put should strictly be used for inserting.

Why would a second operator automatically double the number of notations? Why couldn’t it just add one more notation?
Also, for the purposes of this discussion, I’m not concerned with the implementation details. I’m only interested in understanding how Elixir came to the conclusion to omit the insert syntax.