Re: [boost] metactrl header [compile time asserts]

From: Greg Colvin (greg_at_[hidden])
Date: 2000-07-23 19:03:28

From: David Abrahams <abrahams_at_[hidden]>
> The template mechanism is equivalent to a functional programming language.
> What is this construct called in Lisp? Ugh, I think it's called 'if'.

The more traditional form is 'cond', but the syntax is a little different.

> What is the ?: operator called in C/C++?

From the standard --

  conditional-expression:
          logical-or-expression
          logical-or-expression ? expression : assignment-expression

> BTW, I attended a Generic Programming conference with C&E in '98
> http://www.cs.rpi.edu/~musser/gp/dagstuhl/gpdag.html where they talked about
> generative programming. Most of it seemed to be a pile of buzzwords and
> excitement with little to back it up, but they did present a complete lisp
> interpreter implemented at compile-time with C++ templates!

Now that's cool.  Got a link?  Or do I have to get the book?

> From: "Greg Colvin" <greg_at_[hidden]>
> > From: David Abrahams <abrahams_at_[hidden]>
> > > I totally support all of Howard's arguments below :)
> >
> > Me too.  But what names to use?  Howard's names for 'IF'
> > don't make it so clear what the meaning of the parameters
> > is.  Maybe 'If' would do?
> >
> > Or if we are feeling very brave, how about something like
> >    #define If whatever<
> >    #define Then ,
> >    #define Else ,
> >    #define End >::type
> > so that instead of the inscrutable
> >    typedef If<flag, type1, type2>::type my_type;
> > we can write
> >    typedef
> >       If flag Then
> >          type1
> >       Else
> >          type2
> >       End
> >    my_type;
> >
> > And Howard thought he was getting punchy!

No comment, eh?