Crazy OCaml dynamic evaluation: is this legal (defined behaviour)?

[Gopiandcode]

@art-w

Hm well what’s the type definition of env? Haha wait, are you procedurally generating those lines in the dynamic eval:

    | `Var "a" -> MkWrap (env#a)
    | `Var "i" -> MkWrap (env#i)

Haha, yes, exactly - I was planning on generating a custom evaluation function each time I had a new evaluation context, however…

@art-w

Such that the predicates can then get access to the arbitrary variables that they expect from the env? Then the problem is still not the full blown eval, but only the dispatching of the variables’ values from their names. Perhaps this would work with some more Obj.magic on the host when calling the env dispatch function:

type whatever

fun expr ->
  (* ... *)
  expr (function | "a" -> Obj.magic a
                 | "i" -> Obj.magic i
                 | _   -> (assert false : whatever))

Good point - thanks for the pointer - you’re entirely correct, the use of an object for the environment is actually pretty overkill. I guess I can write a single evaluator function in the host context, no dynamic evaluation, and just defer handling environment variables to it.

@art-w

but you might discover that Obj.magic is unspecified if you keep using it)

I’m curious if anyone in the OCaml community could give some more advice on this.