On 20 March 2014 17:41, Jared Grubb <jared.grubb@gmail.com> wrote:
A couple months back, Andrew Barnet brought up the idea of adding a way to apply functions in an infix style. It really didnt gain much traction. (Subject line "Infix Functions")
Nathaniel Smith has just proposed a PEP to add an infix matrix multiply operator, and everyone seems to love it.
I honestly am surprised at the difference in reaction. Why are we so quick to add a single-purpose punctuation mark, but reject a named infix operator that works for many general cases? Is the matrix-multiply use case so special?
Yes, basically - a large portion of the PEP is about pointing out that matrix multiplication really is that special. All past attempts at getting syntax for it *have* been generalised along that lines of this suggestion from Andrew, and have ended up failing on the grounds of "just use a method or function instead". Nathaniel's PEP is about looking at those past proposals and the experience of the numeric computing community and asking "Which operator have we *really* missed?". And they realised that it was only one: a way to spell matrix multiplication, since "*" has already been claimed for element-wise multiplication. The generalised proposals failed because they were still clumsy for the matrix multiplication use case, and there wasn't a compelling justification for the extra complexity that came with the generalisation. By contrast, Nathaniel's latest PEP looked at solving the *exact* problem the numeric community has: a clean and concise way to spell matrix multiplication. It hit the sweet spot of design proposals: a clean targeted solution that is as simple as it can possibly be, while still solving the problem that needs to be solved. It may have *looked* deceptively fast in terms of core devs saying "yes, that's a good idea", but the speed makes more sense if you start the timer from some of the earlier PEPs referenced from Nathaniel's one - the "matrix multiplication is clumsy compared to MATLAB" problem has been around for as long as people have been doing numeric computing in Python. Cheers, Nick.
I dont oppose the PEP, and I dont mean to derail it. And I know there was quite a bit of discussion on Andrew's email. But I cant help feel that Andrew's idea didnt get the appreciation it should. (But hey, I'm biased because I like the idea :))
Jared
QUICK SUMMARY OF ANDREW'S EMAIL: (Not a proposal for syntax or naming)
m `cross` n m `dot` n
a `Pair` b a `Tree` (b `Tree` c `Tree` d) `Tree` e
And of course the matrix multiply (and matrix div that was briefly discussed) are implementable too:
m `mmul` n m `mdiv` n
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