Re: [Caml-list] how to convert strings to Ocaml values at run-time?

[Matthias Puech <puech@pps.univ-paris-diderot.fr>]

Hi,
I am not sure if I understand your question correctly, but I guess you 
could:
- lex/parse the string to an untyped type of AST [term] as usual, and then
- have the type checking function take a [term] and produce an AST 
annotated with types ['a typed_term]. This type could be either:
     - a GADT, in which case you would need an evaluation function [eval 
: type a. a typed_term -> a], by recursion on the typed term
     - or, à la Finally Tagless [1], an abstract type declared in a 
module together with values implementing the various primitives.

The thing to remember here I think is to "box" the type ['a] of the 
expression parsed into a type annotation, i.e., ['a typed_term]. 
However, I fear it is going to be difficult to extend this approach to 
polymorphism.

Hope it helps,
     -m

[1]: http://okmij.org/ftp/tagless-final/#tagless-final

On 02/23/2014 09:24 PM, Matej Kosik wrote:
> On 23/02/14 13:12, Tianyi Cui wrote:
>> If you know the type of this string in advance, you can do so with ocaml_plugin: https://github.com/janestreet/ocaml_plugin
> Hm, imagine that the expected type is:
>
> 	'a * 'a -> bool
>
> Now, if user provides a string, say:
>
> 	"fun (a,b) -> a = b"
>
> how can I convert that string to Ocaml value of the above type (like how toplevel does it)?
>
> Is this something ocaml_plugin is able to do for me? I've failed to figure out the trick.
>