Toploop.setvalue

Toploop.setvalue

[Roland Zumkeller]

Hi,

Can Toploop.setvalue be used to bind a value to an identifier, as does "let"?

# Toploop.setvalue "b" (Obj.repr 43);;
- : unit = ()
# b;;
Unbound value b

I only got the other direction to work:

# let a = 42;;
val a : int = 42
# (Obj.obj (Toploop.getvalue "a") : int);;
- : int = 42

Best,

Roland

Re: [Caml-list] Toploop.setvalue

[Dave Benjamin]

Roland Zumkeller wrote:
> Hi,
> 
> Can Toploop.setvalue be used to bind a value to an identifier, as does "let"?
> 
> # Toploop.setvalue "b" (Obj.repr 43);;
> - : unit = ()
> # b;;
> Unbound value b
> 
> I only got the other direction to work:
> 
> # let a = 42;;
> val a : int = 42
> # (Obj.obj (Toploop.getvalue "a") : int);;
> - : int = 42

Not that I know of. I was only able to get it to rebind values that I 
initialized by evaluating expressions like "let b = 43;;". Here's an 
example:

http://pleac.sourceforge.net/pleac_ocaml/strings.html#AEN68

Hope this helps - and if anyone has better advice I'd love to hear it,
Dave

Re: Toploop.setvalue

[Zheng Li]

Hello,

On 3/8/2009 10:43 PM, Roland Zumkeller wrote:
> Can Toploop.setvalue be used to bind a value to an identifier, as does "let"?

No. I don't think it's intended to be used in this way.

> # Toploop.setvalue "b" (Obj.repr 43);;
> - : unit = ()
> # b;;
> Unbound value b

This will only inject the value into the runtime, it won't add the 
necessary information into the compiler's working environment. So "b" is 
only visitable through the Toploop.getvalue, not through the normal 
toplevel.

> I only got the other direction to work:
>
> # let a = 42;;
> val a : int = 42
> # (Obj.obj (Toploop.getvalue "a") : int);;
> - : int = 42

In this case, you define a binding the normal way, so both the compiler 
and the runtime knows it. You can visit "a" via both the 
Toploop.getvalue and the normal toplevel.

I don't really understand what purpose you want to achieve, so I can 
only answer your question literally.

HTH.

--
Zheng