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

[Yaron Minsky <yminsky@janestreet.com>]

Indeed, the implementation from that post did make it into
Core_kernel.  Here's the link:

https://github.com/janestreet/core_kernel/blob/release-112.01.00/lib/core_list.ml#L380

y

On Sun, Sep 28, 2014 at 3:45 PM, Malcolm Matalka <mmatalka@gmail.com> wrote:
> https://blogs.janestreet.com/optimizing-list-map/
>
> And from the horse's mouth:
>
> https://groups.google.com/forum/#!msg/fa.caml/YaLYqkpn928/1jdo8a0K6AEJ
>
> Shuai Wang <wangshuai901@gmail.com> writes:
>
>> 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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