Re: [Caml-list] stl?

[Yoann Padioleau <padator@wanadoo.fr>]

Jon Harrop <jon@ffconsultancy.com> writes:

> On Wednesday 04 March 2009 16:48:18 Yoann Padioleau wrote:
>> I don't think so. I've read the last "history of C++" by Stroustrup
>> in HOPL-III, who discusses quite a lot about the STL and Stepanov,
>> and from what I remember unboxing was a big issue
>> and having "generic" (which is slightly different from polymorphic)
>> algorithms without introducing performance
>> penalty that object-solution has with dynamic dispatch was also
>> a big issue. Those people are not stupid.
>
> If they were not stupid, why were their innovations were dropped, e.g. Java, 
> C# and even VB.NET 

First, who cares about Java or C# or VB.NET ? Last time I checked,
all the software I use on my machine (linux, mozilla, apache, mysql, emacs, 
X-windows, gtk, gnome, git, transmission, ...) are written in 
C and sometimes C++ (well except the beautiful ocamlopt and ocamldebug).
>From what I know, most Microsoft software are still written in C++
(Office, Visual Studio, the kernel, etc), and most Apple software
too (with sometimes some objective C stuff). Do we have an example
of a Java killer-app ?

> provide parametric polymorphism from ML (aka generics) 
> instead of C++ templates?

But haven't they added generics in Java because Java programmers
wanted some of the capabilities of C++ templates ? They even
use its syntax, and recent Java has added some ugly extensions
with some star-stuff around it that I don't understand. So I think
Java generics are closer to C++ templates than ML parametric polymorphism
and its inference. 

And Java has decided to not follow C++ on many things, they also
don't have overloading, they have a GC, etc. It's just not the
same target.

>
>> They know about ML.
>
> IIRC Alex Stepanov claimed to know ML but then made a series of factually 
> incorrect statements about it, e.g. "phantom types do not exist". 

I know ML and I don't know those phantom types thing. And if they are
"phantom", isn't he right indeed that they do not actually exist ? 

Do ML designers really know C++ and all its lastest features too 
as in C++0x ?

> His 
> published work includes nothing on anything related to ML:
>
>   http://www.stepanovpapers.com/
>
> I do not believe they knew about ML.

I think at least Stroustrup mentions in its "the design and
evolution of C++" book some comparisons with ML. 
But probably at that time ML didn't
have yet the functor stuff, just the parametric polymorphism. 



>
>> C++ even has some advanced dependent types in some way (array<n>).
>
> I would not call it "advanced". C++'s type system was accidentally Turing 
> complete in a very practically limited way.
>
> Haskell is similar in this respect: check Oleg's 600-line GHC-extended Haskell 
> equivalent of the OCaml code:
>
>   `a
>
> That's what the "power" of Turing completeness buys you.

:) Indeed. Many of those typing-guru tricks are as ugly and incomprensible 
than all the tricks people use with C++ expression templates.


>
>> I hate C++ with a passion, but the C++ designers are far from stupid.
>
> C++ is the pedagogical example of bad language design. 

That's what I was thinking before reading Stroustrup's HOPL-III paper
where you can a chance to get inside the head of stroustrup and the
rationale for many of his decisions. 

Stroustrup wanted a transition path from C to OO, and he wanted
to make that possible without introducing any bit of performance
penalty versus a hand crafted C program, because he knew
the programmers he targeted were really stubborn on performance
and then even a 1% overhead would not be accepted (you can call
those programmers morons, but that's the kind of people he 
wanted to have an impact on). He succeeded. 

> I've learned about 20 
> programming languages now and every one taught me something new. C++ taught 
> me what happens when you let idiots loose on programming language design and 
> get industry to hype the result regardless of its objective value.

C++ taught me that if you want to be really successful, you need a migration
path (or you need to wait for old programmers to die or that a
very different kind of platform arrives so that legacy code 
does not matter any more, e.g. the web).

>
> I'm very happy to see C++ dying.

Is it ? 

>
>> > Scripting languages were not so hot at the time, short of Perl, but
>> > Ruby would easily fit well into the STL idea, just like Lisp also did.
>>
>> No, because of the performance penalty of dispatch. Again, those C++
>> designer guys have strong requirments on performance.
>
> Their performance requirements were: destroy the performance of anything we 
> are not familiar with in order to preserve the performance of familiar 
> features 
> regardless of the relative merits of the different approaches. That 
> is really stupid and very counter productive, of course.

Did Stroustrup did that ? I never saw Stroustrup criticizing
other languages (but I've seend many Java people trashing C++).

>
>> Most of us can live with those overheads, but apparently they don't.
>
> No, we don't just live with the overheads. We reap the benefits of objectively 
> well-engineered features like fast exceptions and fast garbage collection 
> that C++ is incapable of.
>
> -- 
> Dr Jon Harrop, Flying Frog Consultancy Ltd.
> http://www.ffconsultancy.com/?e
>
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