RE: [Caml-list] Re: Toplevel question ...

RE: [Caml-list] Re: Toplevel question ...

[Harrison, John R]

Tomasz Zielonka writes:

> > Is there some alias in toplevel for the result of last evaluation so one
> > could use it instead of retyping (there's no history completion :() and
> > binding to some name?

I don't think so, but I also wish there were. Some other implementations
of ML automatically bind the result of the previous evaluation to a
special identifier "it", treating an expression "E" as "let it = E". This
is really useful if, like me, you work in the toplevel a lot and often
want to evaluate ad hoc chains of dependent expressions.

Even if the OCaml developers don't want to add this feature to the
default toplevel, it must be very easy to support using Camlp4. Perhaps
Daniel de Rauglaudre or another expert can tell us how?

John.
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Re: [Caml-list] Re: Toplevel question ...

[Daniel de Rauglaudre]

Hi,

On Mon, Mar 04, 2002 at 09:10:16AM -0800, Harrison, John R wrote:

> Even if the OCaml developers don't want to add this feature to the
> default toplevel, it must be very easy to support using Camlp4. Perhaps
> Daniel de Rauglaudre or another expert can tell us how?

$ cat it.ml
#load "pa_extend.cmo";
#load "q_MLast.cmo";
open Pcaml;
EXTEND
  top_phrase:
    [ [ sti = str_item; ";;" ->
          match sti with
          [ <:str_item< $exp:e$ >> -> Some <:str_item< value it = $e$ >>
          | x -> Some x ] ] ]
  ;
END;

$ ocamlc -pp camlp4r -I +camlp4 -c it.ml

$ ocaml
        Objective Caml version 3.04+6 (2002-02-05)

# #load "camlp4o.cma";;
        Camlp4std Parsing version 3.04+6 (2002-02-05)

# #load "it.cmo";;
# 2 + 2;;
val it : int = 4

-- 
Daniel de RAUGLAUDRE
daniel.de_rauglaudre@inria.fr
http://cristal.inria.fr/~ddr/
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[Caml-list] Re: Toplevel question ...

[Andrzej M. Ostruszka]

On Fri, Mar 01 (2002), Tomasz Zielonka wrote:
> > Is there some alias in toplevel for the result of last evaluation so one
> > could use it instead of retyping (there's no history completion :() and
> > binding to some name?
> 
> Lack of history can be easily solved - use ledit:

I'll use this mail as an opportunity to thank to all who suggested me
ledit cause this somewhat improves situation but it is still not what I
wanted :) (I want to avoid recomputing of the result).

If there no solution for it then I'll force myself to think before
typing (which I belive is not that bad policy :)) and bind result if it
can cost much of the cputime.

					Best regards
-- 
    ____   _  ___
   /  | \_/ |/ _ \		Andrzej Marek Ostruszka
  / _ |     | (_) | Instytut Fizyki, Uniwersytet Jagiellonski (Cracow)
 /_/ L|_|V|_|\___/	(PGP <-- finger ostruszk@order.if.uj.edu.pl)
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