Re: [Gretl-devel] matrix multiplication question

On Sun, 25 Sep 2011, Summers, Peter wrote: > Allin et al, > > <quote> > Proper addition is of course commutative, but the "extended > addition" that I'm talking about here maybe is not. I tend to think > of the left-hand operand as the "posit", so to speak, and the > right-hand operand as the increment (or decrement, in the case of > subtraction). And I reckon I can attach a good sense to the case > where an m x n matrix is the posit and the increment or decrement is > a scalar (applied to all elements of the posit). But I feel queasy > about the case where the posit is a scalar value and the > increment/decrement is an m x n matrix. This seems a step too far. > > This may become moot if we decide to tighten up and insist on the > dot operators, but I thought I'd just mention it. > </quote> > > My first thought is that if the manual says (mxn) + scalar is > allowed, then the order shouldn't matter. Addition is addition. > Plus (so to speak), the alternative you suggest is afaik different > from the treatments in Matlab, Gauss, etc. So I think if you want > to insist on left-vs-right positioning, that should be documented. Thanks, Peter, that's a useful perspective: what other software does is certainly relevant.