Re: Proposal: add lists:intersperse/2 and lists:intercalate/2

For Haskell's intersperse, we have lists:join/2.
add-between offers rather more options, but that's Racket for you.

On Wed, 24 Mar 2021 at 09:18, Siraaj Khandkar <[email protected]> wrote:

> Greetings Erlangers,
>
> Nothing serious, just some fun here. I stumbled on the function
> "add-between" in Racket stdlib, which reminded me of the lively, lolzy
> debate we had here 5 years ago :-D
>
>      $ racket
>      Welcome to Racket v7.9 [bc].
>      > (add-between '(a b c d) 0)
>      '(a 0 b 0 c 0 d)
>      >
>
>
> https://docs.racket-lang.org/reference/pairs.html#%28def._%28%28lib._racket%2Flist..rkt%29._add-between%29%29
>
>
> On 3/2/16 12:02 PM, Siraaj Khandkar wrote:
> > On 3/2/16 9:47 AM, Jesper Louis Andersen 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?
> >
> > +1
> >
> > Though I prefer the name "interleave" to "intersperse", since its
> > meaning is more-precise and closer to the intended behavior here.
>