[Caml-list] Re: findlib-0.8.1 and ocaml-3.07+beta1

[Caml-list] Re: findlib-0.8.1 and ocaml-3.07+beta1

[james woodyatt]

On Thursday, Jul 24, 2003, at 06:38 US/Pacific, Gerd Stolpmann wrote:
> Am Don, 2003-07-24 um 08.29 schrieb james woodyatt:
>>
>> I think there might be something bolluxed in findlib-0.8.1 with
>> ocaml-3.07+beta1.  I compiled and installed ocaml-3.07+beta1 on Mac OS
>> X 10.2.6 with December 2002 developer tools (gcc version 3.1 
>> 20020420),
>> and it seems to work fine.
>>
>> But findlib-0.8.1 seems not to behave properly.
>
> Both problems are caused by an interface change in the module Arg. 
> [...]
> Here is a patch so the beta testers can continue. Apply it with
> patch -p0 <patch

Applying this patch works for me.

I ran into only two problems making my current project compile and work 
against the new beta1 version of ocaml-3.07:

+ The word 'parser' is a keyword again.  So I had to change the names 
of a class and some values to not conflict.

+ The ocamlmklib now makes dynamic libraries on Mac OS X, and that 
means I had to fix my build-and-install recipe to handle that fact.  
Figuring it out was a little tricky.  The error message "Error on 
dynamically loaded library: cannot access this bundle" is a little 
cryptic.  I had to change the source code to tell me which library 
before I could understand why its image wasn't being mapped.  I wasn't 
copying dllfoo.so into its location next to libfoo.a, and fixing that 
made everything better.

By the way, HUGE PHAT PROPS to the Caml Team for some of the new 
language features, not to mention the dynamic linking love for Mac OS 
X.  I'm excited.  I'm specifically excited about the polymorphic 
generalization of covariant parts of expansive expressions.  Believe it 
or not.  I think it might simplify some of my code dramatically.


-- 
j h woodyatt <jhw@wetware.com>
that's my village calling... no doubt, they want their idiot back.

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Re: [Caml-list] Re: findlib-0.8.1 and ocaml-3.07+beta1

[Karl Zilles]

james woodyatt wrote:
> I'm specifically excited about the polymorphic 
> generalization of covariant parts of expansive expressions.  

I read about this in the changes document, but I'm unable to wrap my 
head around it.

 > For instance, if f: unit -> 'a list, "let x = f ()"
 > gives "x" the generalized type forall 'a. 'a list, instead of '_a list
 > as before.

Can someone simplify this for me?  Under what circumstances would this 
be useful?

Karl

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Re: [Caml-list] Re: findlib-0.8.1 and ocaml-3.07+beta1

[james woodyatt]

On Thursday, Jul 24, 2003, at 18:28 US/Pacific, Karl Zilles wrote:
> james woodyatt wrote:
>> I'm specifically excited about the polymorphic generalization of 
>> covariant parts of expansive expressions.
>
> I read about this in the changes document, but I'm unable to wrap my 
> head around it.
>
> > For instance, if f: unit -> 'a list, "let x = f ()"
> > gives "x" the generalized type forall 'a. 'a list, instead of '_a 
> list
> > as before.
>
> Can someone simplify this for me?  Under what circumstances would this 
> be useful?

Sure.  I see it with functors.  Consider the following example:

	# module type X = sig
	    type +'a t
	    val f: unit -> 'a t
	  end;;

This is a module type I plan to use as the input to a functor.  The top 
responds with this following:

	module type X = sig type +'a t val f : unit -> 'a t end

So, imagine you want to write a functor like so:

	# module Y(X: X) = struct
	    let x = X.f ()
	  end;;

Here's what the 3.06 top-level says is the type of that module:

	module Y : functor (X : X) -> sig val x : '_a X.t end

Here's what the 3.07+beta1 version says:

	module Y : functor (X : X) -> sig val x : 'a X.t end

This is so much better.  In the 3.06 case, I get a module whose type 
isn't complete yet.  In the 3.07+beta1 case, I get a module whose type 
is complete.  With 3.06, I have to write 'x' as a function that returns 
a constructed object every time I call it.  With 3.07+beta1, I can 
write 'x' as a value that gets constructed once when the functor is 
called.


-- 
j h woodyatt <jhw@wetware.com>
that's my village calling... no doubt, they want their idiot back.

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Re: [Caml-list] Re: findlib-0.8.1 and ocaml-3.07+beta1

[pjd]

> X.  I'm excited.  I'm specifically excited about the polymorphic
> generalization of covariant parts of expansive expressions.

That might explain my apparent lack of progress with ocaml.
Perhaps one needs to be a maths graduate and a mensa member to appreciate
the language ?

:-)

pj

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