[erlang-questions] Proposal: add lists:intersperse/2 and lists:intercalate/2

Jesper Louis Andersen jesper.louis.andersen@REDACTED
Mon Apr 11 14:06:27 CEST 2016

Reviving this. There is now a PR for the proposal:


The name is hard. I'm on the verge of asking Robert Virding what it should
be and then use him as the BDFL. I'm not going to ask Joe, since then we
would have disagreement between him and Robert :)

On Wed, Mar 2, 2016 at 3:47 PM, Jesper Louis Andersen <
jesper.louis.andersen@REDACTED> wrote:

> Hi Erlangers,
> I'd really like to add two functions to the lists module from Haskell:
> intersperse(List, Seperator) produces a list where each element is
> separated by separator, i.e.
> X = [1,2,3]
> [1, x, 2, x, 3] = lists:intersperse(X, x),
> and it's cousin, intercalate(ListOfLists, Separator) is
> append(intersperse(ListOfLists, Seperator)), i.e,
> Y = ["a", "b", "c"]
> "a, b, c" = lists:intercalate(Y, ", "),
> The implementations are straightforward and easy to write tests for, even
> property based tests if needed.
> The rationale for this proposal is that I find myself implementing this
> function again and again in every project I write, and it is highly
> generic. It belongs in a typical list module. OCaml libraries add it.
> Haskell's Data.List has it. I believe Erlang, being a practical language,
> should have it as well.
> Thoughts?
> --
> J.

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