[erlang-questions] trouble with erlang or erlang is a ghetto

Jesper Louis Andersen jesper.louis.andersen@REDACTED
Thu Jul 28 12:37:15 CEST 2011

On Thu, Jul 28, 2011 at 04:28, Jon Watte <jwatte@REDACTED> wrote:

> All modern languages have a simple hash map class that is efficient and
> built-into the language. JavaScript, Python, Ruby, etc.
> In Erlang, we have dict, and gb_tree, and proplist, and ets, but none of
> them are as easy to use, and some of them have performance problems once you
> scale over a few dozen or a few hundred elements, and others (ets) are way
> overkill for this particular use case.
> Or would anyone want to argue that "dict" is actually as good/productive as
> JavaScript objects or Python dicts?

JavaScript, Python, Ruby, etc almost all have ephemeral dict
structures. In Erlang, the structure must be persistent, like in
Clojure/Haskell and so on. This rules out a number of possible

As it stands, "dict" is probably the right replacement, with gb_trees
for some situations as they have different speed in those. The "dict"
does fairly well, but it is implemented in Erlang and fast as it is,
it cannot compete with a C-implementation of a ephemeral structure.

Should we want to BIF/NIFify such a structure, I'd recommend either a
patricia hash table or a HAMT. In fact, that would be an interesting
thing to try. Though I wonder how much I can alter the in-memory
structure of the tree from Erlang terms - I'd really like some cache
efficient packing there for tree nodes.


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