Immediate recursive functions

Immediate recursive functions

[Alex Baretta]

I sometimes feel the need for a mu operator. I'm thinking of something 
like the following:

# (rec f x -> if x <= 0 then 1 else x * (f (pred x))) 5
- : int = 120

as opposed to

(let rec f x = if x <= 0 then 1 else x * (f (pred x)) in f) 5
- : int = 120

This is not really a feature wish so much a bit of insane curiosity. Is 
there any specific reason for not having this in the core language syntax?

Alex

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Re: [Caml-list] Immediate recursive functions

[Marcin 'Qrczak' Kowalczyk]

Alex Baretta <alex@barettadeit.com> writes:

> I sometimes feel the need for a mu operator. I'm thinking of something
> like the following:
>
> # (rec f x -> if x <= 0 then 1 else x * (f (pred x))) 5
> - : int = 120
>
> as opposed to
>
> (let rec f x = if x <= 0 then 1 else x * (f (pred x)) in f) 5
> - : int = 120

Here it is immediately applied to arguments. For such cases my
language Kogut provides a syntax:

   loop 5 [
      x {if (x <= 0) {1} else {x * again (x - 1)}}
   ]

or with pattern matching:

   loop 5 [
      (<= 0) {1}
      x      {x * again (x - 1)}
   ]

This is related to 'case' (OCaml's 'match') like in Scheme "named let"
is related to ordinary 'let', except that the name 'again' is implicit.
There can be more arguments than one.

-- 
   __("<         Marcin Kowalczyk
   \__/       qrczak@knm.org.pl
    ^^     http://qrnik.knm.org.pl/~qrczak/

Re: [Caml-list] Immediate recursive functions

[Jason Hickey]

Alex Baretta wrote:
> I sometimes feel the need for a mu operator. I'm thinking of something 
> like the following:
> 
> # (rec f x -> if x <= 0 then 1 else x * (f (pred x))) 5
> - : int = 120
...
> This is not really a feature wish so much a bit of insane curiosity. Is 
> there any specific reason for not having this in the core language syntax?

I can't give any arguments why your specific syntax is not allowed.  In 
principle it isn't necessary, since a general fixpoint can be defined.

# let rec fix f x = f (fix f) x;;
val fix : (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b = <fun>
# fix (fun f i -> if i = 0 then 1 else i * f (i - 1)) 10;;
- : int = 3628800
# fix (fun f i j -> if i = 0 then 1 else j * f (i - 1) j) 10 5;;
- : int = 9765625

The drawback is that (fix f x) is likely to be a bit more expensive to 
evaluate than the let-rec version.

Jason

-- 
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Caltech Computer Science      Tel: 626-395-6568 FAX: 626-792-4257

Re: [Caml-list] Immediate recursive functions

[Alex Baretta]

Jason Hickey wrote:
> Alex Baretta wrote:
> 
>> I sometimes feel the need for a mu operator. I'm thinking of something 
>> like the following:  ..
>
> I can't give any arguments why your specific syntax is not allowed.  In 
> principle it isn't necessary, since a general fixpoint can be defined.

Why, of course it isn't needed! Neither is let rec needed for that 
matter once you have the fun construct. Y-combinators are all around you ...

Of course, a large number of language features are just syntactic sugar 
which boils down to lambda abstractions and beta reductions. Explicit 
recursion is one of these. What I'm asking for is why the language does 
not provide the sugar for the mu recursive expressions.

Alex

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Re: [Caml-list] Immediate recursive functions

[Christian Szegedy]

Alex Baretta wrote:

> I sometimes feel the need for a mu operator. I'm thinking of something 
> like the following:
>
> # (rec f x -> if x <= 0 then 1 else x * (f (pred x))) 5
> - : int = 120
>
> as opposed to
>
> (let rec f x = if x <= 0 then 1 else x * (f (pred x)) in f) 5
> - : int = 120

Feel free to write your CamlP4 extension ;)

Re: [Caml-list] Immediate recursive functions

[Alex Baretta]

Christian Szegedy wrote:
> Alex Baretta wrote:
> 
>> I sometimes feel the need for a mu operator. I'm thinking of something 
>> like the following:
>>
>> # (rec f x -> if x <= 0 then 1 else x * (f (pred x))) 5
>> - : int = 120
>>
>> as opposed to
>>
>> (let rec f x = if x <= 0 then 1 else x * (f (pred x)) in f) 5
>> - : int = 120
> 
> 
> Feel free to write your CamlP4 extension ;)

I have had a short love story with Camlp4, but I find it's syntax far 
too wild to be worth learning. Hence, I abandoned camlp4 except for its 
ocpp incarnation with its quotation expansion support.

I have written a short patch to parsing/parser.mly to support my syntax, 
but I am unable to get anything sensible out of it. I'll look more into 
this problem and post the patch if I manage to figure things out.

Alex

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Camlp4 documentation (was: Immediate recursive functions)

[Martin Jambon]

On Thu, 17 Feb 2005, Christian Szegedy wrote:

> Feel free to write your CamlP4 extension ;)

:-)
But there are few things to know/discover before starting.

Is anyone interested in a kind of highly practical tutorial on
how to extend the syntax of OCaml with Camlp4?
I could possibly start writing one if there is enough demand.


Martin

--
Martin Jambon, PhD
Researcher in Structural Bioinformatics since the 20th Century
The Burnham Institute http://www.burnham.org
San Diego, California

Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[Richard Jones]

On Thu, Feb 17, 2005 at 02:39:12PM -0800, Martin Jambon wrote:
> But there are few things to know/discover before starting.
> 
> Is anyone interested in a kind of highly practical tutorial on
> how to extend the syntax of OCaml with Camlp4?
> I could possibly start writing one if there is enough demand.

Definitely!

Rich.

-- 
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Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[Michael Walter]

Yes! :)


On Thu, 17 Feb 2005 23:30:20 +0000, Richard Jones <rich@annexia.org> wrote:
> On Thu, Feb 17, 2005 at 02:39:12PM -0800, Martin Jambon wrote:
> > But there are few things to know/discover before starting.
> >
> > Is anyone interested in a kind of highly practical tutorial on
> > how to extend the syntax of OCaml with Camlp4?
> > I could possibly start writing one if there is enough demand.
> 
> Definitely!
> 
> Rich.
> 
> --
> Richard Jones, CTO Merjis Ltd.
> Merjis - web marketing and technology - http://merjis.com
> Team Notepad - intranets and extranets for business - http://team-notepad.com
> 
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Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[Micha]

Am Donnerstag, 17. Februar 2005 23:39 schrieb Martin Jambon:
> Is anyone interested in a kind of highly practical tutorial on
> how to extend the syntax of OCaml with Camlp4?
> I could possibly start writing one if there is enough demand.

yes :-)

 Michael

Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[briand]

I would also be interested.

brian

Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[Oliver Bandel]

On Thu, Feb 17, 2005 at 02:39:12PM -0800, Martin Jambon wrote:
> On Thu, 17 Feb 2005, Christian Szegedy wrote:
> 
> > Feel free to write your CamlP4 extension ;)
> 
> :-)
> But there are few things to know/discover before starting.
> 
> Is anyone interested in a kind of highly practical tutorial on
> how to extend the syntax of OCaml with Camlp4?

absolutely, there is....


I neglected Camlp4 because of the uncomprehensible
documentation on it.



> I could possibly start writing one if there is enough demand.

DEMAND!
DEMAND!
DEMAND!
DEMAND!


Regards,
   Oliver

Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[Johann Spies]

On Thu, Feb 17, 2005 at 02:39:12PM -0800, Martin Jambon wrote:
> On Thu, 17 Feb 2005, Christian Szegedy wrote:
> 
> > Feel free to write your CamlP4 extension ;)
> 
> :-)
> But there are few things to know/discover before starting.
> 
> Is anyone interested in a kind of highly practical tutorial on
> how to extend the syntax of OCaml with Camlp4?

Yes, please.

Regards
Johann

-- 
Johann Spies          Telefoon: 021-808 4036
Informasietegnologie, Universiteit van Stellenbosch

     "All we like sheep have gone astray; we have turned 
      every one to his own way; and the LORD hath laid on 
      him the iniquity of us all."         Isaiah 53:6 

Re: [Caml-list] Camlp4 documentation

[Alex Baretta]

Martin Jambon wrote:
> On Thu, 17 Feb 2005, Christian Szegedy wrote:
> 
> 
>>Feel free to write your CamlP4 extension ;)
> 
> 
> :-)
> But there are few things to know/discover before starting.
> 
> Is anyone interested in a kind of highly practical tutorial on
> how to extend the syntax of OCaml with Camlp4?
> I could possibly start writing one if there is enough demand.
> 
> 
> Martin
> 

Why yes! Yet, it's terribly sad that DdR chose to forcibly impose upon 
the Camlp4 metaprogrammer to use the revised syntax. This is probably 
the main obstacle, together with the relative lack of documentation, to 
the diffusion of Camlp4, IMHO.

Alex

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Re: [Caml-list] Camlp4 documentation

[Alex Cowie]

Alex Baretta wrote:

> Martin Jambon wrote:
>
>> On Thu, 17 Feb 2005, Christian Szegedy wrote:
>>
>>
>>> Feel free to write your CamlP4 extension ;)
>>
>>
>>
>> :-)
>> But there are few things to know/discover before starting.
>>
>> Is anyone interested in a kind of highly practical tutorial on
>> how to extend the syntax of OCaml with Camlp4?
>> I could possibly start writing one if there is enough demand.
>>
>>
>> Martin
>>
>
> Why yes! Yet, it's terribly sad that DdR chose to forcibly impose upon 
> the Camlp4 metaprogrammer to use the revised syntax. This is probably 
> the main obstacle, together with the relative lack of documentation, 
> to the diffusion of Camlp4, IMHO.
>
> Alex
>
For me, the use of revised syntax has been a disincentive to using 
Camlp4 metaprogramming.  I have always wondered whether a traditional 
syntax version of Camlp4 was technically feasible.  Any comments?

Alex Cowie

--
School of Computer and Information Science
University of South Australia

Camlp4 with traditional syntax (was: Camlp4 documentation)

[Hendrik Tews]

Alex Cowie <cowie@cs.unisa.edu.au> writes:

   For me, the use of revised syntax has been a disincentive to using
   Camlp4 metaprogramming.  I have always wondered whether a traditional
   syntax version of Camlp4 was technically feasible.  Any comments?

I believe it is possible. You can parse traditional ocaml (as
opposed to the revised syntax) with camlp4, so it should be
possible to write a quotation expander using traditional ocaml. I
remember Daniel de Rauglaudre complaint a few times about the
difficulty of parsing ocaml. So a quotation expander using
traditional ocaml might have dark corners which do not look as
elegant as pa_macro.ml.

A alternative quotation expander using traditional ocaml would be
much simpler to set up than the original one in
camlp4/meta/q_MLast, because you don't have to deal with
bootstrapping issues. The alternative expander would be written
in the revised syntax and compiled when camlp4 has been built.

Moreover, all the necessary pieces are already contained in the
camlp4 sources: the quotation expander is in q_MLast and the
traditional ocaml syntax is in etc/pa_o.ml. So you would only mix
the two files, taking the grammer from pa_o and the actions from
q_MLast.

I even started once, but did not continue. If anybody starts to
work on an alternative quotation expander using traditional
ocaml, please announce.

Bye,

Hendrik Tews

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Alex Baretta]

Hendrik Tews wrote:
> Alex Cowie <cowie@cs.unisa.edu.au> writes:
> 
>    For me, the use of revised syntax has been a disincentive to using
>    Camlp4 metaprogramming.  I have always wondered whether a traditional
>    syntax version of Camlp4 was technically feasible.  Any comments?
> 
> I believe it is possible. You can parse traditional ocaml (as
> opposed to the revised syntax) with camlp4, so it should be
> possible to write a quotation expander using traditional ocaml. I
> remember Daniel de Rauglaudre complaint a few times about the
> difficulty of parsing ocaml. So a quotation expander using
> traditional ocaml might have dark corners which do not look as
> elegant as pa_macro.ml.

There is one more issue with Camlp4: it does not allow for quotations to 
expand to generic syntactic elements. Often, I use quotations which 
expand to module definitions. I had to implement my own quotation 
expander, bypassing the limitations of Camlp4 to achieve this.

Alex


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Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Hendrik Tews]

Alex Baretta <alex@barettadeit.com> writes:

   There is one more issue with Camlp4: it does not allow for quotations
   to expand to generic syntactic elements. Often, I use quotations which
   expand to module definitions. I had to implement my own quotation
   expander, bypassing the limitations of Camlp4 to achieve this.
   
I don't quite understand, what's wrong with 

let me = <:module_expr< struct $ list of module def's $ end >>
in
  <:str_item< module $some_name$ = $me$ >> 

??

Bye,

Hendrik

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Alex Baretta]

Hendrik Tews wrote:
> Alex Baretta <alex@barettadeit.com> writes:
> 
>    There is one more issue with Camlp4: it does not allow for quotations
>    to expand to generic syntactic elements. Often, I use quotations which
>    expand to module definitions. I had to implement my own quotation
>    expander, bypassing the limitations of Camlp4 to achieve this.
>    
> I don't quite understand, what's wrong with 
> 
> let me = <:module_expr< struct $ list of module def's $ end >>
> in
>   <:str_item< module $some_name$ = $me$ >> 

We use quotation expanders to embed completely different languages, such 
as SQL, within Ocaml code. Specifically, the SQL quotation expander 
compiles SQL code to an Ocaml module. CamlP4 signals an error because 
quotations are only meant to be used as expressions or as patterns, 
IIRC. Anyhow, the solution is either to use ocpp rather than camlp4 as a 
preprocessor (ocpp is less picky), or to write one's own quotation 
preprocessor. We use both techniques depending on the context.

Alex


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Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Bardur Arantsson]

On Mon, Feb 21, 2005 at 01:28:25PM +0100, Alex Baretta wrote:

> Hendrik Tews wrote:
> >Alex Baretta <alex@barettadeit.com> writes:

> >   There is one more issue with Camlp4: it does not allow for quotations
> >   to expand to generic syntactic elements. Often, I use quotations which
> >   expand to module definitions. I had to implement my own quotation
> >   expander, bypassing the limitations of Camlp4 to achieve this.

> >I don't quite understand, what's wrong with 

> >let me = <:module_expr< struct $ list of module def's $ end >>
> >in
> >  <:str_item< module $some_name$ = $me$ >> 

> We use quotation expanders to embed completely different languages, such 
> as SQL, within Ocaml code. Specifically, the SQL quotation expander 
> compiles SQL code to an Ocaml module. CamlP4 signals an error because 
> quotations are only meant to be used as expressions or as patterns, 
> IIRC.

IIRC quotations can expand to arbitrary ASTs. Only the point of *use*
(ie. substitution) determines which types of ASTs will be accepted.

Of course, if you're generating things like module interfaces and
implementations, you'll need to generate them side by side since there is
no "combined module interface+implementation" AST node type.

-- 
Bardur Arantsson
<bardur@imada.sdu.dk>
<bardur@scientician.net>

Intolerant people should be shot.

Re: [Caml-list] Camlp4 with traditional syntax

[Olivier Andrieu]

 > Bardur Arantsson [Mon, 21 Feb 2005]:
 > On Mon, Feb 21, 2005 at 01:28:25PM +0100, Alex Baretta wrote:
 > 
 > > Hendrik Tews wrote:
 > > >Alex Baretta <alex@barettadeit.com> writes:
 > 
 > > >   There is one more issue with Camlp4: it does not allow for quotations
 > > >   to expand to generic syntactic elements. Often, I use quotations which
 > > >   expand to module definitions. I had to implement my own quotation
 > > >   expander, bypassing the limitations of Camlp4 to achieve this.
 > 
 > > >I don't quite understand, what's wrong with 
 > 
 > > >let me = <:module_expr< struct $ list of module def's $ end >>
 > > >in
 > > >  <:str_item< module $some_name$ = $me$ >> 
 > 
 > > We use quotation expanders to embed completely different
 > > languages, such as SQL, within Ocaml code. Specifically, the SQL
 > > quotation expander compiles SQL code to an Ocaml module. CamlP4
 > > signals an error because quotations are only meant to be used as
 > > expressions or as patterns, IIRC.
 > 
 > IIRC quotations can expand to arbitrary ASTs. Only the point of
 > *use* (ie. substitution) determines which types of ASTs will be
 > accepted.

No, quotations can expand to only expressions or patterns. See the
type of a quotation expander in quotation.mli :

  type expander =
  | ExStr of (bool -> string -> string)
  | ExAst of ((string -> MLast.expr) * (string -> MLast.patt))

As Alex mentionned, ocpp expands quotations everywhere (but only deals
with string-expanding quotations, not the AST ones), so it can be used
to generate structure items (module elements).

 > Of course, if you're generating things like module interfaces and
 > implementations, you'll need to generate them side by side since
 > there is no "combined module interface+implementation" AST node
 > type.

The camlp4 AST does have this kind of nodes, as Martin mentionned.
You can use :

# fun a b -> <:str_item< declare $a$ ; $b$ ; end >> ;;
- : MLast.str_item -> MLast.str_item -> MLast.str_item = <fun>

or :

# fun l -> <:str_item< declare $list:l$ end >> ;;
- : MLast.str_item list -> MLast.str_item = <fun>

-- 
   Olivier

Re: [Caml-list] Camlp4 with traditional syntax

[Bardur Arantsson]

On Mon, Feb 21, 2005 at 04:22:24PM +0100, Olivier Andrieu wrote:

>  > Bardur Arantsson [Mon, 21 Feb 2005]:
>  > On Mon, Feb 21, 2005 at 01:28:25PM +0100, Alex Baretta wrote:

>  > > Hendrik Tews wrote:
>  > > >Alex Baretta <alex@barettadeit.com> writes:

>  > > >   There is one more issue with Camlp4: it does not allow for quotations
>  > > >   to expand to generic syntactic elements. Often, I use quotations which
>  > > >   expand to module definitions. I had to implement my own quotation
>  > > >   expander, bypassing the limitations of Camlp4 to achieve this.

>  > > >I don't quite understand, what's wrong with 

>  > > >let me = <:module_expr< struct $ list of module def's $ end >>
>  > > >in
>  > > >  <:str_item< module $some_name$ = $me$ >> 

>  > > We use quotation expanders to embed completely different
>  > > languages, such as SQL, within Ocaml code. Specifically, the SQL
>  > > quotation expander compiles SQL code to an Ocaml module. CamlP4
>  > > signals an error because quotations are only meant to be used as
>  > > expressions or as patterns, IIRC.

>  > IIRC quotations can expand to arbitrary ASTs. Only the point of
>  > *use* (ie. substitution) determines which types of ASTs will be
>  > accepted.

> No, quotations can expand to only expressions or patterns. See the
> type of a quotation expander in quotation.mli :

>   type expander =
>   | ExStr of (bool -> string -> string)
>   | ExAst of ((string -> MLast.expr) * (string -> MLast.patt))

> As Alex mentionned, ocpp expands quotations everywhere (but only deals
> with string-expanding quotations, not the AST ones), so it can be used
> to generate structure items (module elements).

You're right. I got confused by the distinction between user-defined and
pre-defined quotation expanders.

>  > Of course, if you're generating things like module interfaces and
>  > implementations, you'll need to generate them side by side since
>  > there is no "combined module interface+implementation" AST node
>  > type.

> The camlp4 AST does have this kind of nodes, as Martin mentionned.
> You can use :

> # fun a b -> <:str_item< declare $a$ ; $b$ ; end >> ;;
> - : MLast.str_item -> MLast.str_item -> MLast.str_item = <fun>

> or :

> # fun l -> <:str_item< declare $list:l$ end >> ;;
> - : MLast.str_item list -> MLast.str_item = <fun>

Uh, yes, you use <str_item:<...> to generate module implementations, but 
when I looked last you couldn't use MLast.sig_item and MLast.str_item
interchangably, so for instance, you couldn't ask pr_(o|r) to
pretty-print a str_item as a module interface. Instead you had to also
generate a sig_item and pretty-print that. (For good reason, you don't
necessarily want to have everything inside the module visible from the
outside...). That's all I was referring to by generating them "side by
side".

-- 
Bardur Arantsson
<bardur@imada.sdu.dk>
<bardur@scientician.net>

- It might look like I'm standing motionless, but I'm actively
waiting for my problems to go away.
                                                      Scott Adams

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Martin Jambon]

On 18 Feb 2005, Hendrik Tews wrote:

> Alex Cowie <cowie@cs.unisa.edu.au> writes:
>
>    For me, the use of revised syntax has been a disincentive to using
>    Camlp4 metaprogramming.  I have always wondered whether a traditional
>    syntax version of Camlp4 was technically feasible.  Any comments?
>
> I believe it is possible. You can parse traditional ocaml (as
> opposed to the revised syntax) with camlp4, so it should be
> possible to write a quotation expander using traditional ocaml. I
> remember Daniel de Rauglaudre complaint a few times about the
> difficulty of parsing ocaml. So a quotation expander using
> traditional ocaml might have dark corners which do not look as
> elegant as pa_macro.ml.

There is (at least) one construct which is not provided by the regular
syntax (because it is totally useless when writing code by hand) but
which is essential:

  declare <list of str_items> end

This just packs several definitions (str_items) as one single
str_item.
This is extremely useful when replacing one definition written in an
extended syntax by several successive definitions (or zero) written in
OCaml.


Martin

--
Martin Jambon, PhD
Researcher in Structural Bioinformatics since the 20th Century
The Burnham Institute http://www.burnham.org
San Diego, California

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Hendrik Tews]

Martin Jambon <martin_jambon@emailuser.net> writes:

   There is (at least) one construct which is not provided by the regular
   syntax (because it is totally useless when writing code by hand) but
   which is essential:
   
     declare <list of str_items> end
   
Right, the ocaml in the alternative quotation expander would have
to get enriched with some pieces of the revised syntax. But
that is easy to implement.

Bye,

Hendrik

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Oliver Bandel]

On Fri, Feb 18, 2005 at 05:20:34PM +0100, Hendrik Tews wrote:
> Alex Cowie <cowie@cs.unisa.edu.au> writes:
> 
>    For me, the use of revised syntax has been a disincentive to using
>    Camlp4 metaprogramming.  I have always wondered whether a traditional
>    syntax version of Camlp4 was technically feasible.  Any comments?
> 
> I believe it is possible. You can parse traditional ocaml (as
> opposed to the revised syntax) with camlp4, so it should be
> possible to write a quotation expander using traditional ocaml. I
> remember Daniel de Rauglaudre complaint a few times about the
> difficulty of parsing ocaml. So a quotation expander using
> traditional ocaml might have dark corners which do not look as
> elegant as pa_macro.ml.
[...]


Because I don't know about what you all are talking here,
I hope that the intended Camlp4-Tutorial will explain
such things in more detail.

Not another "we know nearly all, and explain some nifty
details, that you also can see, when looking into the sources
and study them some months/years" documentation, please... :->

So, if the indended doc on Camlp4 would
explain in detail what it is good for, what it
provides and how to use it, I (and IMHO many others)
would gain a lot of such a documentation/tutorial.

Explaining the details to pwople who already knew
the most stuff, IMHO is not really needed. This can be
done in discussions on the list (or when people
know the tools, they really can look into the sources,
because they know something about what they are intended to do).

Hoping for a good intruductional tutorial...

Regards,
  Oliver

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Richard Jones]

On Tue, Feb 22, 2005 at 11:29:00AM +0100, Oliver Bandel wrote:
> So, if the indended doc on Camlp4 would
> explain in detail what it is good for, what it
> provides and how to use it, I (and IMHO many others)
> would gain a lot of such a documentation/tutorial.

I too am eagerly awaiting a good tutorial on Camlp4.  I've done a few
things using Camlp4, and for me the syntax seems to be needlessly
obscure.  For example, here's how to write an infix 'map_with'
operator, the syntax being: 'list map_with f' which is equivalent to
'List.map f list':

open Pcaml

EXTEND
   expr: AFTER "apply"
   [ LEFTA
       [ e1 = expr; "map_with"; e2 = expr ->
           <:expr< List.map $e2$ $e1$ >>
       ]
   ];
END

Rich.

-- 
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
Team Notepad - intranets and extranets for business - http://team-notepad.com

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Martin Jambon]

On Tue, 22 Feb 2005, Oliver Bandel wrote:

[...]
> Because I don't know about what you all are talking here,
> I hope that the intended Camlp4-Tutorial will explain
> such things in more detail.

I started writing a tutorial this weekend. There are many things to say,
and there are also many things that I ignore...

> Not another "we know nearly all, and explain some nifty
> details, that you also can see, when looking into the sources
> and study them some months/years" documentation, please... :->
>
> So, if the indended doc on Camlp4 would
> explain in detail what it is good for, what it
> provides and how to use it, I (and IMHO many others)
> would gain a lot of such a documentation/tutorial.

I will try to talk about just what I know, not give too many technical
details but rather pointers to the relevant sources of documentation or
tips on "What should do in that case?".

The goal is just to avoid anyone being stuck more than 2 minutes while
trying to extend the syntax of OCaml.

> Explaining the details to pwople who already knew
> the most stuff, IMHO is not really needed. This can be
> done in discussions on the list (or when people
> know the tools, they really can look into the sources,
> because they know something about what they are intended to do).
>
> Hoping for a good intruductional tutorial...

OK, I will try my best.


Martin

--
Martin Jambon, PhD
Researcher in Structural Bioinformatics since the 20th Century
The Burnham Institute http://www.burnham.org
San Diego, California

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[Oliver Bandel]

On Tue, Feb 22, 2005 at 04:01:05PM -0800, Martin Jambon wrote:
> On Tue, 22 Feb 2005, Oliver Bandel wrote:
> 
> [...]
> > Because I don't know about what you all are talking here,
> > I hope that the intended Camlp4-Tutorial will explain
> > such things in more detail.
> 
> I started writing a tutorial this weekend. There are many things to say,
> and there are also many things that I ignore...
> 
> > Not another "we know nearly all, and explain some nifty
> > details, that you also can see, when looking into the sources
> > and study them some months/years" documentation, please... :->
> >
> > So, if the indended doc on Camlp4 would
> > explain in detail what it is good for, what it
> > provides and how to use it, I (and IMHO many others)
> > would gain a lot of such a documentation/tutorial.
> 
> I will try to talk about just what I know, not give too many technical
> details but rather pointers to the relevant sources of documentation or
> tips on "What should do in that case?".
> 
> The goal is just to avoid anyone being stuck more than 2 minutes while
> trying to extend the syntax of OCaml.

Sounds good. :)


Hint:

   "Just as a picture is worth a thousands words,
    so is a properly chosen program example."

         (Stephen G. Kochan, Programming in Objective C, page 2)


> 
> > Explaining the details to pwople who already knew
> > the most stuff, IMHO is not really needed. This can be
> > done in discussions on the list (or when people
> > know the tools, they really can look into the sources,
> > because they know something about what they are intended to do).
> >
> > Hoping for a good intruductional tutorial...
> 
> OK, I will try my best.

:)


Ciao,
   Oliver

Re: [Caml-list] Camlp4 with traditional syntax (was: Camlp4 documentation)

[William D. Neumann]

On Thu, 24 Feb 2005, Oliver Bandel wrote:

> Hint:
>
>   "Just as a picture is worth a thousands words,
>    so is a properly chosen program example."
>
>         (Stephen G. Kochan, Programming in Objective C, page 2)

And if I might add, in the other direction:

     "But a poorly chosen program example is not
      even worth the number of tokens it contains."

           (William D. Neumann, This e-mail, page 1)

William D. Neumann

---

"There's just so many extra children, we could just feed the
children to these tigers.  We don't need them, we're not doing 
anything with them.

Tigers are noble and sleek; children are loud and messy."

         -- Neko Case

  Think of XML as Lisp for COBOL programmers.

 	-- Tony-A (some guy on /.)

Re: [Caml-list] Camlp4 documentation (was: Immediate recursive functions)

[Robert M. Solovay]

I would greatly appreciate such a tutorial.

	--Bob Solovay


On Thu, 17 Feb 2005, Martin Jambon wrote:

> On Thu, 17 Feb 2005, Christian Szegedy wrote:
>
> > Feel free to write your CamlP4 extension ;)
>
> :-)
> But there are few things to know/discover before starting.
>
> Is anyone interested in a kind of highly practical tutorial on
> how to extend the syntax of OCaml with Camlp4?
> I could possibly start writing one if there is enough demand.
>
>
> Martin
>
> --
> Martin Jambon, PhD
> Researcher in Structural Bioinformatics since the 20th Century
> The Burnham Institute http://www.burnham.org
> San Diego, California
>
>
> _______________________________________________
> Caml-list mailing list. Subscription management:
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>

Camlp4 documentation

[Jon Harrop]

Are the constructions listed here:

  http://caml.inria.fr/pub/docs/manual-camlp4/manual010.html

valid for the new camlp4 as well?

For example, <:expr< ( $list:el$ ) >> to deconstruct a tuple.

If not, is there equivalent up-to-date documentation anywhere?

-- 
Dr Jon Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/?e

Re : [Caml-list] Camlp4 documentation

[Matthieu Wipliez]

Most of them are.

A tuple is represented as <:expr< ($e$) >> for instance, as can be seen on the Wiki page Abstract Syntax Tree:

    http://brion.inria.fr/gallium/index.php/Abstract_Syntax_Tree


Cheers,

Matthieu



----- Message d'origine ----
> De : Jon Harrop <jon@ffconsultancy.com>
> À : caml-list@inria.fr
> Envoyé le : Samedi, 23 Mai 2009, 14h24mn 45s
> Objet : [Caml-list] Camlp4 documentation
> 
> 
> Are the constructions listed here:
> 
>   http://caml.inria.fr/pub/docs/manual-camlp4/manual010.html
> 
> valid for the new camlp4 as well?
> 
> For example, <:expr< ( $list:el$ ) >> to deconstruct a tuple.
> 
> If not, is there equivalent up-to-date documentation anywhere?
> 
> -- 
> Dr Jon Harrop, Flying Frog Consultancy Ltd.
> http://www.ffconsultancy.com/?e
> 
> _______________________________________________
> Caml-list mailing list. Subscription management:
> http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list
> Archives: http://caml.inria.fr
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs

Re: Re : [Caml-list] Camlp4 documentation

[Christophe TROESTLER]

On Sat, 23 May 2009 13:13:23 +0000, Matthieu Wipliez wrote:
> 
> A tuple is represented as <:expr< ($e$) >> 

Well, at the moment, the better is to complement the information on
the wiki with personal experiments in the toploop (and occasionally
read the Camlp4 sources).  For example, for the above assertion:

  #directory "+camlp4";;
  #load "dynlink.cma";;  (* OCaml >= 3.11.0 *)
  #load "camlp4of.cma";;
  open Camlp4.PreCast;;
  let _loc = Loc.ghost;;
  
  open Syntax;;

  # let f e = <:expr< ($e$) >>;;
  val f : 'a -> 'a = <fun>

With such a signature, you can imagine that f is just the identity
function and you can confirm it with a few experiments.  To match a
tuple, first look how they are represented:

  let e = <:expr< x,y,z >>;;
  val e : Camlp4.PreCast.Syntax.Ast.expr =
    Camlp4.PreCast.Syntax.Ast.ExTup (<abstr>,
     Camlp4.PreCast.Syntax.Ast.ExCom (<abstr>,
      Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
       Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "x")),
      Camlp4.PreCast.Syntax.Ast.ExCom (<abstr>,
       Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
        Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "y")),
       Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
        Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "z")))))
  
Tuples are thus constructed with "ExTup" which is matched by $tup$ :

  # match e with <:expr< $tup:t$ >> -> t;;
  - : Camlp4.PreCast.Syntax.Ast.expr =
  Camlp4.PreCast.Syntax.Ast.ExCom (<abstr>,
   Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
    Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "x")),
   Camlp4.PreCast.Syntax.Ast.ExCom (<abstr>,
    Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
     Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "y")),
    Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
     Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "z"))))

Then you probably want the individual components that are separated by
comas.  You can easily write your own function but looking at the
Camlp4 sources, you will find that it is already provided :

  # match e with <:expr< $tup:t$ >> -> Ast.list_of_expr t [];;
  - : Camlp4.PreCast.Syntax.Ast.expr list =
  [Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
    Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "x"));
   Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
    Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "y"));
   Camlp4.PreCast.Syntax.Ast.ExId (<abstr>,
    Camlp4.PreCast.Syntax.Ast.IdLid (<abstr>, "z"))]

Hope it helps,
C.

Re: [Caml-list] Camlp4 documentation

[Jon Harrop]

On Saturday 23 May 2009 18:37:21 Christophe TROESTLER wrote:
> Tuples are thus constructed with "ExTup" which is matched by $tup$ :

How did you determine that they are matched with $tup$?

> Hope it helps,

It does, thank you.

-- 
Dr Jon Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/?e

Re: [Caml-list] Camlp4 documentation

[Christophe TROESTLER]

On Sat, 23 May 2009 20:22:38 +0100, Jon Harrop wrote:
> 
> On Saturday 23 May 2009 18:37:21 Christophe TROESTLER wrote:
> > Tuples are thus constructed with "ExTup" which is matched by $tup$ :
> 
> How did you determine that they are matched with $tup$?

Frankly I can't remember.  Possibly in camlp4 sources or in a
discussion.

Regards,
C.