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

[Siraaj Khandkar]

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.