Re: [Caml-list] ocaml{c,opt} choked

[Nicolas Braud-Santoni <nicolas.braudsantoni@gmail.com>]

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On 25/01/2014 19:39, Matej Kosik wrote:
> Hi,
>
> I am using ocaml 4.01.0.
>
> I have noticed the following strange behavior:
> [...]
>
> I would like to ask: is this is a known phenomenon?
> -------------------------------------------------------------------
> The context:
>
> I have started to apply the advice given here:
> https://sympa.inria.fr/sympa/arc/caml-list/2013-11/msg00207.html
> That way I've got terms with which ocaml{c,opt} struggles.

Hi,

It is a well-known problem that type inference is exponential-type[0]
This worst-case behaviour is triggered when you have deeply nested -> in
the types.

For an example, consider :

let f x y = y x x in
let g x = f (f x) in
let h x = g (g x) in
let h x = h (h x) in
let h x = h (h x) in
h;; (* This actually causes a stack overflow *)


Unfortunately, there isn't (as far as I know) a silver bullet.
Avoiding deep nesting of combinators mights be a solution, though.
I usually also helps with readability.

Regards,
Nicolas

[0] under ETH, probably, but I don't currently remember.


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