[Caml-list] Why List.map does not be implemented tail-recursively?

[Shuai Wang <wangshuai901@gmail.com>]

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Hello list,


I am working on some stack_overflow exception in our recent project written
in OCaml
and eventually it turns out that this exception is thrown by List.map
function.

By seeing the source code of OCaml's List module
<https://code.ohloh.net/file?fid=P5Us_txNCMHIhpdfML6OZ8QN4Zs&cid=Jigg8RAfQdg&s=ocaml%20list.ml&pp=0&fp=305967&fe=ml&ff=1&filterChecked=true&mp=1&ml=1&me=1&md=1#L3>,
it seems that map function
does not be implemented tail-recursively:

let rec map f = function
    [] -> []
  | a::l -> let r = f a in r :: map f l



So my question is:

*Why would OCaml's implementation List.map like this?  *

In my humble option, it definitely should be written in a tail-recursive
way,
and it not, stack_overflow would be unavoidable.
For example in order to handle the exception,
I abandon the code using List.map and rewrite it into a tail-recursive help
function.

Best,
Shuai

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