John~
It can be made to sort of work. Consider the following
struct point {
double x;
double y;
};
struct circle {
point center;
double radius;
}
boolean contains(circle c, point p) {
double dx = c.center.x * p.x;
double dy = c.center.y * p.y;
double dist2 = dx*dx + dy*dy;
return dist2 < c.radius*c.radius;
}
This example can be made to work by statically expanding center into
circle and then rewriting c.center.* to access the expanded fields.
The following, however, cannot be made to work (without a data copy):
boolean foo(circle c1, circle c2) {
return contains(c1, c2.center);
}
The problem is the access to c2.center as a top-level structure.
Recall from the previous step that you had to expand its field's into
the top level structure. In the case where a struct contains at most
1 other struct, you can cheat and use inheritance to get the correct
behavior, but that is a total hack and does not work in the general
case. What you would need to do, is generate a method to pack
circle's center fields into a point struct on demand. This would
incur a data-copy when you directly reference a sub-struct, but the
common case of only accessing leaves would still be able to implement
efficiently. For more deeply nested structures, recurse ;-)
Matt
On Mon, Dec 7, 2009 at 1:01 PM, John Wilson <[email protected]> wrote:
> I don't think you can do this in a straightforward way (but possibly
> somebody will be long soon to enlighten both of us!).
>
> When I want a large number of identical "structures" in Java I use an
> array of arrays. Would this work for you?
>
>
> John Wilson
>
> --
>
> You received this message because you are subscribed to the Google Groups
> "JVM Languages" group.
> To post to this group, send email to [email protected].
> To unsubscribe from this group, send email to
> [email protected].
> For more options, visit this group at
> http://groups.google.com/group/jvm-languages?hl=en.
>
>
>
--
You received this message because you are subscribed to the Google Groups "JVM
Languages" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/jvm-languages?hl=en.
