Maybe that's already implicit in the broadcasting proposal but it
wouldn't hurt to spell it out:
A dimension size of 1 should be broadcasted to match that of the
other operand. So, for example, the following shapes (returned by
@#array) are compatible:
@c = @a * @b
result shape shape @a shape @b
[4,8,5] [4,1,5] [4,8,5]
[5,3,2] [1,3,2] [5,1,2]
In that respect it would be nice to have a slicing syntax to introduce
'dummy' dimensions of size 1 (e.g. Yorick uses the concept of a
pseudo-index, [1]; similarly NumPy [2]; PDL has dummy dimensions via '*'
using C<slice>):
@a = sin @x; # 1D array
@b = cos @x;
@twod = @a * @b[-;];
which would be the same as
@twod[|i;|j] = @a[|i] * @b[|j];
Christian
[1] ftp://ftp-icf.llnl.gov/pub/Yorick/ydoc/manual/Pseudo-Index.html
[2] http://numpy.sourceforge.net/numdoc/HTML/numdoc.html#pgfId-36371
--
Christian Soeller [EMAIL PROTECTED] x2770
Dept. of Physiology U. Auckland School of Medicine
Auckland New Zealand
