Re: [Caml-list] OCaml related article

Re: [Caml-list] OCaml related article

[Jan Skibinski]

On Sun, 22 Apr 2001, Jonathan Coupe wrote:

> Mark J Dominus' excellent discussion of ML's type system (written for Perl
> programmers..) is available at:
> http://perl.plover.com/yak/typing/typing.html

	His conclusion though is that it is practically impossible
	to introduce any kind of static typing to Perl. Contrast it
	with http://www.cc.gatech.edu/~lex/ti/ti.html
	where Lex Spoon attempts to deliver a type inference engine to
	Smalltalk (sic!).

	Jan


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[Caml-list] OCaml related article

[Jonathan Coupe]

Mark J Dominus' excellent discussion of ML's type system (written for Perl
programmers..) is available at:
http://perl.plover.com/yak/typing/typing.html

Jonathan Coupe

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Re: [Caml-list] OCaml related article

[Jan Skibinski]

On Mon, 23 Apr 2001, Xavier Leroy wrote:


> .. and since Smalltalk
> has cleaner, more restrictive dynamic semantics than Perl, it could
> actually be useful in finding errors.

	I believe the other motivations are: to improve on documentation
	(consistent naming policy is often not enough since it's tough to
	enforce it in a consistent and yet readable way) to ease a
	process of learning of a third party code and, first of all, to
	have a tool helping to identify/create some sort of modular
	structures within a given image.

	To elaborate a bit on the last point:
	As far as I know, inheritance is often being overused - resulting
	in some artificial relashionships, which create some delivery
	problems: how does one reduce the image size without removing
	one class or one method too many? This is often a lengthy
	post-mortem exercise - even though Smalltalk has variety of
	excellent tools to help with such tasks. 

	Jan

 

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Re: [Caml-list] OCaml related article

[Xavier Leroy]

> 	His conclusion though is that it is practically impossible
> 	to introduce any kind of static typing to Perl.

Dominus' claim is that if it could be done, it would still be largely
useless: since Perl has so many context-dependent automatic coercions,
nearly all programs would be correct, and the type system wouldn't
help much finding programming errors.

Actually, I believe one could do a soft typing system for Perl along
the lines of Mr. Spidey for Scheme
(http://www.cs.rice.edu/CS/PLT/packages/mrspidey/), using
constraint-based flow analysis.  Of course, uses of "eval" would not
be checked at all.  But Dominus' point that it would be largely
useless is probably true.

>       Contrast it
> 	with http://www.cc.gatech.edu/~lex/ti/ti.html
> 	where Lex Spoon attempts to deliver a type inference engine to
> 	Smalltalk (sic!).

Why not?  Constraint-based flow analysis can be applied to Smalltalk
(at least without the reflection features -- if you change the
behavior of method invocation, all bets are off), and since Smalltalk
has cleaner, more restrictive dynamic semantics than Perl, it could
actually be useful in finding errors.

- Xavier Leroy
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