Re: operator overloading
On Wed, 21 May 2008, Mark Space wrote:
Tom Anderson wrote:
On Tue, 20 May 2008, Mark Space wrote:
I also think that perhaps some sort of matrix semantics could be provide
for some sort of abstract number class, again using []. This wasn't
brought up much, but thinking on it I believe it might be useful.
It wouldn't be. Do you declare the operator in the interfaces - List, Map,
Set - or not? If no, only in AbstractList etc, then users have to declare
their variables as AbstractList, rather than List. That sucks. If yes, then
users can't define their own implementations of List, because they can't
write an implementation of the [] method. That also sucks.
No, as a subclass of AbstractNumber; eg. AbstractMatrix or something like
that.
Aaargh, for some reason, i thought we were talking about collections. I'm
sure someone mentioned collections. Dammit.
I'd like to see it support ',' in the [], ie.
MyMatrix m = new MyMatrix(3,3); // 2 dimensions
m[0,0] = 0.5;
To implement this, you'd have to pay attention to eliminating unnecessary
object creation. The only general way to implement arbitrary sized
dimensions is through some sort of variable arguments scheme
public abstract class AbstractMatrix<class T> {
T get( int ... i );
void put( T t, int ... i );
}
But this would require the compiler to generate an anonymous array for
each invocation, which could kill performance.
Have more faith in the compiler! The escape analysis for that array is
probably going to be pretty simple, so there's a good chance it could be
passed on the stack.
However, I think most practical applications of matrices require only
one or two dimensions. So if the compiler had the option to chose a
faster operation for those types of matrices, then it might be
practical.
public abstract class AbstractMatrix<class T> {
T get( int i );
T get( int i, int j );
T get( int ... i );
void put( T t, int i );
void put( T t, int i, int j);
void put( T t, int ... i );
}
Now we have some practical options for small matrices, and a CYA
implementation for arbitrarily large matrices.
Hmm. What happens if i call get(int) on my three-dimensional matrix?
Can we not have Vector, Matrix2d, Matrix3d, MultidimensionalMatrix? Is it
so important to only have one class for all of them?
tom
--
[Philosophy] is kind of like being driven behind the sofa by Dr Who -
scary, but still entertaining. -- itchyfidget