On Sat, Mar 15, 2014 at 7:01 PM, Alexander Belopolsky <ndarray@mac.com> wrote:
On Sat, Mar 15, 2014 at 2:25 PM, Alexander Belopolsky <ndarray@mac.com> wrote:
On Fri, Mar 14, 2014 at 11:41 PM, Nathaniel Smith <njs@pobox.com> wrote:
Here's the main blocker for adding a matrix multiply operator '@' to Python: we need to decide what we think its precedence and associativity should be.
I am not ready to form my own opinion, but I hope the following will help shaping the discussion.
One more question that I think should be answered by the PEP and may influence the associativity decision is what happens if in an A @ B @ C expression, each operand has its own type that defines __matmul__ and __rmatmul__? For example, A can be an ndarray, B a sympy expression and C a pyoperator.
The general rule in Python is that in a binary operation A # B, then first we try A.__special__, and if that doesn't exist or it returns NotImplemented, then we try B.__rspecial__. (The exception is that if B.__class__ is a proper subclass of A.__class__, then we do it in the reverse order.) -- Nathaniel J. Smith Postdoctoral researcher - Informatics - University of Edinburgh http://vorpus.org