Re: [boost] Felix linux demo available/Tuple Review

From: John Max Skaller (skaller_at_[hidden])
Date: 2001-06-20 16:53:33

Gary Powell wrote:
> 
> Hi,
> 
> [John Max Skaller]
> Felix is new programming language designed for C++ programmers.
> It generates C++, and has a lot of features you've always wanted. :-)
> 
> [Gary]
> I noticed that Felix has "tuples", if boost::tuple was zero based, and had
> pointer to member access, would you use it in the Felix "compiler"?

        I don't think I could use it for the native tuple
type, it's too closely integrated into the compiler.
For example, I need to create a list of offsets to any
pointers so the garbage collector will work: the technology
uses 

        offsetof(S,mem)

However, I could certainly build a binding.
Felix is designed for genericity, but it isn't implemented,
so I'll illustrate with tuple<int, float>:

        header """
        #include <boost/tuples>
        using namespace boost::tuples;
        """
        #include <std.flx> // for int, float, etc

        type tuple_i_f = "tuple<int,float>";
        fun get_first : tuple_i_f -> int = "get<1>($1)";
        fun get_second : tuple_i_f -> float = "get<2>($1)";
        fun mktuple : int * float -> tuple_i_f = "mk_tuple($1,$2)";

        val t = mktuple(1,2.0);
        val x = t.first;
        val y = t.second;

Note that 't.first' expands to 'get_first(t)'.

> I'm just looking for a justification for doing this work.

        IMHO: Don't change anything unless you're
totally convinced.

        By the way, the way tuples are implemented
using a recursive type is very clever. It has got
me thinking about a more general solution for C++,
and also Felix.

        What C++ extensions are needed to get
rid of the 'nil' things, and make the templates
work for _arbitrary_ length?

        The answer is strange: we need list operations
at the template level. I don't know exactly what form.

-- 
John (Max) Skaller, mailto:skaller_at_[hidden]
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