Re: [Caml-list] How to write an efficient interpreter

[Gerd Stolpmann <info@gerd-stolpmann.de>]

Am Montag, den 24.10.2011, 14:46 +0200 schrieb oliver:
> On Mon, Oct 24, 2011 at 02:40:13PM +0200, Gerd Stolpmann wrote:
> > Am Montag, den 24.10.2011, 13:50 +0200 schrieb Diego Olivier Fernandez
> > Pons:
> > >      Caml-list,
> > > 
> > > 
> > > Xavier Leroy wrote
> > > > Compiling to bytecode is probably overkill.
> > > 
> > > 
> > > 
> > > I think that writing my own bytecode interpreter is looking for
> > > trouble. Same for compiling to an existing bytecode.
> > > 
> > > 
> > > The language being a kind of SQL, most of the work is to properly
> > > execute the comprehensions (= queries).
> > > 
> > > 
> > > For instance
> > > 
> > > 
> > >      range numbers = 0 .. 100;
> > >      {int}  sqrtLessThan [k in numbers] = { x | x in numbers : x * x
> > > <= k };
> > > 
> > > 
> > > There are smarter ways to implement this than a double loop
> > > 
> > > 
> > > I was rather thinking of translating on-the-fly into Caml code and
> > > letting Caml do the job. Is that technically possible (rewriting a
> > > toplevel ? a CamlP4 grammar ?). If so guess I would have to license
> > > the Caml compiler from the INRIA.
> > 
> > I don't think you need that, because you can load compiled OCaml code
> > dynamically (look into the Dynlink library).
> [...]
> 
> Maybe you both talk about different things...
> 
> What you seem to talk about is not interpreter but compiler stuff,
> and later bind it together?!

Exactly. But what's the big difference? You want to run code of a
domain-specific language.

> I would assume, with "translating on-the-fly into Caml code"
> is something meant that could be done via partial application.

The interpretative overhead does not go away with this technique. E.g.
looking up variables in your interpretation environment. I'd consider
this as a micro-optimization that doesn't bring much improvement.

Gerd

> Parsing the language that you implement, and create partial
> applicated functions of OCaml-code that do the work.
> 
> This can be done straight forward and nearly "ad hoc".
> It's an easy way to go. Yo can create such partial applicated functions
> while prsing or from an AST that you construct in parsing stage.
> 
> Ciao,
>    Oliver
> 

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