Strange, Gmail has cut my example.

Here it is normally.

[1 2]
A = [3 4]

[5 6]
B = [7 8]

[a d]
C = [b c]

(A*B)@C
=
[5  12]   [a d]
[21 32] @ [b c]
=
[5a+12b  5d+12c ]
[21a+32b 21d+32c]

A*(B@C)
=
[1 2]   [5a+6b 5d+6c]
[3 4] * [7a+8b 7d+8c]
=
[5a+6b   10d+12c]
[21a+24b 28d+32c]

2014-03-18 16:29 GMT+01:00 Robert Kern :
On Tue, Mar 18, 2014 at 3:22 PM, Christophe Bal <projetmbc@gmail.com> wrote:
> About weak-left. You need to define a priority of @ the matrix product
> regarding to * the elementwise product because (A*B)@C <> A*(B@C) : see the
> example above. I say that also from a mathematical point of view.

What example above?

> Using mathematical like notations, Matrix1 * Matrix2 * 3 can be written
> because (Matrix1 * Matrix2) * 3 = Matrix1 * (Matrix2 * 3).

This seems to argue against what you just said.

> That's why I think that the weak-left is the better choice.

But this is true as well:

3 * Matrix1 * Matrix2 = (3 * Matrix1) * Matrix2 = 3 * (Matrix1 * Matrix2)

Does that expression argue for tight-left?

--
Robert Kern
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