Re: [Caml-list] Accessing values calculated by Toploop.execute_phrase

[Thomas Refis <thomas.refis@gmail.com>]

2016-02-11 14:11 GMT+00:00 Philippe Veber <philippe.veber@gmail.com>:
>   I'm having quite some fun interacting with the toplevel using `Toploop`
> and co., and I am now looking for a way to get the values created during a
> call to `Toploop.execute_phrase`, which sadly only returns a boolean. I
> would like to get these values as `Obj.t` values, so that I could perform
> additional computations for certain types.
>
> I'm almost there but not yet:
>   - I can find which values were created and what's their type by collecting
> `Outcometree.out_path` values when they are printed, but this doesn't give
> access to the actual value (represented as an `Obj.t`).
>   - I could use `Toploop.getvalue`, but then I could not get results of
> evaluations that were not bound to a variable.

Well, you can hack around the final problem by rewriting the
expression you feed to [execute_phrase] so the result is always bound
to a variable.
[Toploop.execute_phrase] already has a bit of code to check whether
the result is a value not bound to any name (
https://github.com/ocaml/ocaml/blob/trunk/toplevel/toploop.ml#L263 ),
you could do something similar on your side. This works on the
typedtree but you can do the same on the parsetree. Or you could type
your expression beforehand, reuse that exact piece of code, but only
when the value is of the type you want (since you apparently want to
do extra computations "for certain types").

Thomas.

PS: https://www.youtube.com/watch?v=p8oi6M4z_e0