[Caml-list] The need for opcode GRAB?

[Caml-list] The need for opcode GRAB?

[A Joseph Koshy]

Perhaps a basic question about the O'Caml bytecode interpreter:

Why do we need to check at runtime if a function is being 
partially applied?  Isn't this information available to the
compiler?

Regards,
Koshy
<koshy@india.hp.com>
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Re: [Caml-list] The need for opcode GRAB?

[Dmitry Lomov]

On Friday 15 November 2002 12:15, A Joseph Koshy wrote:
> Perhaps a basic question about the O'Caml bytecode interpreter:
>
> Why do we need to check at runtime if a function is being
> partially applied?  Isn't this information available to the
> compiler?

No it is not:

implementation A.ml:
let f x y = x + y
let g x = if x = 1 then fun y -> y else fun y -> y - 1

interface A.mli:
val f : int -> int -> int
val g : int -> int -> int

usage (somewhere outside A):
let k = (A.f 1) (* this application is partial *)
let r = (A.g 1) (* this application is not partial *)

Compiler cannot distinguish between those two cases
(knowing only A interface).

BTW a GRAB/RESTART trick is very cool IMHO.
My students always "Wow!" at it. Any references as to
where it comes from (or was it a Xavier's own clever idea?)

Cheers,
Dmitry


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Re: [Caml-list] The need for opcode GRAB?

[Blair Zajac]

Dmitry Lomov wrote:
> 
> On Friday 15 November 2002 12:15, A Joseph Koshy wrote:
> > Perhaps a basic question about the O'Caml bytecode interpreter:
> >
> > Why do we need to check at runtime if a function is being
> > partially applied?  Isn't this information available to the
> > compiler?
> 
> No it is not:
> 
> implementation A.ml:
> let f x y = x + y
> let g x = if x = 1 then fun y -> y else fun y -> y - 1
> 
> interface A.mli:
> val f : int -> int -> int
> val g : int -> int -> int
> 
> usage (somewhere outside A):
> let k = (A.f 1) (* this application is partial *)
> let r = (A.g 1) (* this application is not partial *)
> 
> Compiler cannot distinguish between those two cases
> (knowing only A interface).
> 
> BTW a GRAB/RESTART trick is very cool IMHO.
> My students always "Wow!" at it. Any references as to
> where it comes from (or was it a Xavier's own clever idea?)

What is the grab/restart trick?  Is there a URL to an explanation?

I didn't find anything definitive through Google.

Best,
Blair

-- 
Blair Zajac <blair@orcaware.com>
Web and OS performance plots - http://www.orcaware.com/orca/
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Re: [Caml-list] The need for opcode GRAB?

[Alan Schmitt]

* Blair Zajac (blair@orcaware.com) wrote:
> What is the grab/restart trick?  Is there a URL to an explanation?
> 
> I didn't find anything definitive through Google.
> 
> Best,
> Blair

A long time ago, in a research building far far away, Didier Le Botlan
and me started a small project to explain how ocaml worked, under the
hood. We haven't done anything about for a long time, and it's barely
started but if you want to have a look, here are the html pages:
http://pauillac.inria.fr/~lebotlan/docaml_eng.html

And if anyone wants to contribute, I'd be glad to restart the project.
The sourceforge project page is at:
http://www.sf.net/projects/docaml/

Alan

-- 
The hacker: someone who figured things out and made something cool happen.
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Re: [Caml-list] The need for opcode GRAB?

[Dmitry Lomov]

On Saturday 16 November 2002 03:18, Alan Schmitt wrote:
> A long time ago, in a research building far far away, Didier Le Botlan
> and me started a small project to explain how ocaml worked, under the
> hood. We haven't done anything about for a long time, and it's barely
> started but if you want to have a look, here are the html pages:
> http://pauillac.inria.fr/~lebotlan/docaml_eng.html
>
> And if anyone wants to contribute, I'd be glad to restart the project.
> The sourceforge project page is at:
> http://www.sf.net/projects/docaml/

I guess this would be a very cool resource, but I am afraid I have
enough trouble documenting my own work to start doing this for others :)
Probably Xavier could give a helping hand? ;)

I can try to ask some of my students to TeXize (and translate to English)
their notes, but I do not think they'll agree (I wouldn't :))

Cheers, 
Dmitry
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