Re: [GD-General] Re: C++ turing complete

[Patrick M D. <pa...@wa...>]

On Sun, 23 Dec 2001, Jesse Jones wrote:

> I have a vague recollection of a more practical definition of a
> Turing complete language. It went something like: a language is
> Turing complete if it has sequential statements, some form of if
> statement, and I think one other thing that I can't recall.

Probably recursion - that should be sufficient to make it Turing-complete.
This is a limiting definition though as those behaviors aren't
strictly necessary.

> >Regardless, templates provide an expressive meta-language for static
> >compilation.  I'll admit that I don't fully understand the excitement as
> >one can do this in a more powerful (and understandable) fashion by simply
> >generating C++ code.
>
> Well, there's a lot of value in being able to generate the code from
> within C++. It's more portable and convenient than using something
> like Perl and it's better integrated with the other parts of the
> language.

There other ways to generate code besides Perl--consider a parser
generator like Yacc.  One could probably implement this using template
meta-programming techniques, but I'm sure that Yacc can give much better
error messages and provides a syntax that is easier to use than templates.

Integration with the language is nice, but it's a pity that it comes at
such a high price to the syntax.  This becomes especially noticeable when
compared with similar systems in Lisp or Camlp4.

At least C++ template syntax is not as bad as Unlambda.

Patrick