Re: [Caml-list] Problems with printing MetaOCaml generated code

[Leo White <leo@lpw25.net>]

> Can we talk about what is non-serializable here? I pushed some code to a
> public repo for demonstration purposes. I have a simple interpreter for
> a simple language. I'm experimenting with different levels of
> interpreter specializations(aka. first Futamura projections). As a
> simplest specialization, I want to eliminate parsing costs. The code
> that's supposed to do this is here:
> 
> https://github.com/osa1/int-proj/blob/master/Unlambda.ml#L204
> 
> `p'` in that code is lifted, and it's parsed syntax tree of given source
> file. Syntax tree is defined here:
> 
> https://github.com/osa1/int-proj/blob/master/Syntax.ml#L63
> 
> I think it doesn't have anything that's not serializable: It's just a
> simple monomorphic type, doesn't have any closures etc.
> 
> But MetaOCaml is failing to print this code. To try it yourself, make
> sure you have metaocamlc in $PATH, and run:
> 
>   ➜  unlambda git:(master) ✗ make unlambda_metaocaml
>   metaocamlc -c Syntax.ml
>   metaocamlc Syntax.cmo Unlambda.ml -o unlambda_metaocaml
> 
>   ➜  unlambda git:(master) ✗ ./unlambda_metaocaml programs/Hello.unl stage0
>   File "Unlambda.ml", line 204, characters 67-69:
>   Warning 22: The CSP value is a closure or too deep to serialize
>   File "Unlambda.ml", line 204, characters 58-66:
>   Warning 22: The CSP value is a closure or too deep to serialize
>   .<(* CSP eval_ref *) (* CSP p' *) []>.
> 

From a quick look at the code, it seems pretty clear that `eval_ref` is not serializable.
It is a local function so there is no AST fragment which could represent it globally. I
suspect that if you moved `eval_ref` into a separate module, so that it was
a global function, then this code would work.

Regards,

Leo