From: Christian <christians@...>
Date: 2001-01-16T09:53:11+09:00
Subject: [ruby-talk:9352] Re: 101 Misconceptions About Dynamic Languages


This is largely off-topic. Even so, this is a mailing list regarding an
interpreted language, and the notion of C++ as an interpreted language is
probably of interest to many on this list. That said, if this thread is to
continue it should be moved to private email or another list (suggestions?).

<Josh>
> [ C++ is not type safe because ] it is possible to
> accidentally dereference invalid objects and write
> to invalid memory addresses.
</Josh>

I haven't done that in a long time. Maybe it's because I'm an 'expert'. More
likely it is because I very rarely need pointers (I use containers), I dont
use delete (I use smart pointers), and I dont dereference invalid objects (I
pass arguments by value or reference). And I definitely dont use
explicit_casts. But it's nice to know that I can when I need to.

[skip rant about access to a parser that can be supplied as a library, or by
using ANTLR]

> Christian> What is the practical difference between Managed C++ embedded
in XML and
> >Ruby?
>
> Josh> Managed C++ is apparently a new choice for the interpreted domain;
a
> choice which looks quite similar to C++.  So it can be evaluated
> relative to usual set of criteria:
>
> a) is it cross platform
> b) is it open source
> c) it is fast
> d) is it flexible
> e) is it easy to write wrappers for calling compiled code
> d) is it easy to embed
>
> I don't know the answers to these questions.  Perhaps you
> would like to fill in?

I am no expert on .NET.

a) No, but it is straight forward to make it so. All you need is a virtual
machine that understands IL (intermediate language). A worthy cause for all
the Penguin hax0rs.
b) No, but see a).
c) I haven't done any tests yet, but I've dissasembled M-C++ and looked at
the resultant IL. The JIT compiler produces native code from this IL, and
the IL looks a lot like a generic assembly language with class extensions
and type information. I intend to run some real-world performance analysis.
d) Of course it is flexible -- it is C++ with transparent access to classes,
methods and data defined in other languages, even across process and machine
boundaries.
e) You don't need to 'write a wrapper for calling compiled code'. You just
call it. All of the IL files contain meta-data that describes the interface
to what is in it. You don't need any form of seperate IDL or manual
marshalling.
f) Yes, that's the point. With .NET you can embed C++ into XML. And XML is
(or will be) ubiquitous.

> Templates are cool, but C++ doesn't natively provide much support
> for meta-programming.  Compare C++ with Ruby or Common Lisp
> for the  project of listing and/or serializing and later restoring all
> current system objects.

There is no direct connection between meta-programming (describing types
programmatically rather than explicitly) and persistence (object
serialisation).

C++ does provide native support for meta-programming -- it's called partial
specialisation. Partial specialisation allows you to do some quite
remarkable things. I'd love to elaborate but I feel that I have already
veered enough from Ruby to justifiably invoke the wrath of many on this
list.

Christian