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Date: Mon, 09 Jun 2003 12:56:57 -0400
From: Hyman Rosen <hyrosen@mail.com>
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Subject: Re: Ideas for Ada 200X
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Date: 2003-06-09T12:56:57-04:00
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tmoran@acm.org wrote:
>   I'm confused.  You generate a parse tree at runtime, but the compiler
> takes this runtime result and generates code?  Is this a two-pass process?

Yes, sort of. The parse tree is generated at runtime, but the
overall type of the result is already known at compile-time.
Then inlining generates the code. Let's see if I can code a
relatively simple example:

     template <typename L, typename R>
     struct add_op
     {
         const L &l;
         const R &r;
         add_op(const L &l, const R &r) : l(l), r(r) { }
         double operator()(int i, int j) const
         { return l(i,j) + r(i,j); }
     };

     template <typename L, typename R>
     add_op<L,R> operator+(const L &l, const R &r)
     { return add_op<L,R>(l,r); }

     template <int N>
     struct Matrix
     {
         double data[N][N];

	template <typename T>
         Matrix &operator=(const T &r)
         {
             for (int i = 0; i < M; ++i)
                 for (int j = 0; j < N; ++j)
                     data[i][j] = r(i,j);
             return *this;
         }

         double operator()(int i, int j) const
         { return data[i][j]; }
     };