Re: How to tie

Owen Jacobson <>
Mon, 31 Dec 2007 11:14:33 -0800 (PST)
On Dec 31, 8:10 am, Abble <> wrote:

On Dec 31, 9:53 am, Lew <> wrote:

Abble wrote:

Thanks, Lew, but I'd like if possible to not have to wrap my array.

Why not?

Because I have about 60,000 lines of old code from C, C++, and FORTRAN
with array references like:

    D[i] = A[ i ] + B[i] + C[ i ]; // use A B c

I think to objectize these the lines would look like:

D.setval( i, A.getval( i ) + B.getval( i ) + C.getval( i ) ); // use=

A B c

So the goal is to do whatever it takes so we can keep the natural
array notations and legibility of the expressions( which can get very
long), AND speed would be nice, as the native code C, C++ and FORTRAN
codes are already not as fast as one might like.

You could translate array (or std::vector/std::list) access from C++
to array access in Java, of course, which avoids the verbose-code
"problem". But, to answer your question, no; you can't create new
compile-time names at runtime (and that sentence should probably be
sufficient to explain why not... :). Since the algorithm you're
describing has implicit knowledge of the structure of the data, why
not something like:

  Database db = openDatabase ("foo.xml");
  long[] a = db.getElements ("a"); // or getA ();
  long[] b = db.getElements ("b"); // ibid
  long[] c = db.getElements ("c"); // ibid

  // validate a, b, c here, and determine n
  long[] d = new long[n];

  for (int i = 0; i < n; ++i)
    d[i] = a[i] + b[i] + c[i];


If you really need sparseness, then at least D and probably A, B, and
C would need to be objects of some sparse indexed collection type, in
which case you're kind of back to square one, and there's no way
around it. Java's syntax is not great for purely-numeric programs.

You might have a look at writing the number crunchy bits of the
program in Scala, which targets the JVM and can both call into and be
called from Java classes.

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