Hi, Le 22/03/2014 19:13, Nathaniel Smith a écrit :

After 88 emails we don't have a conclusion in the other thread (see [1] for background). But we have to come to some conclusion or another if we want @ to exist :-). So I'll summarize where the discussion stands and let's see if we can find some way to resolve this. Thanks for this nice summary. I found the previous thread very interesting to follow.

My first reaction when the associativity question was raised was : why would anyone want this non-standard right-associativity ? Indeed, I don't see the special case of Mat*Mat*vec to be important enough to break the common convention. Then, I almost got convinced by the function composition argument. It looks quite elegant, but in the end, there is no current mainstream usage. Also, somebody could use the new @ operator to perform function composition (and not function application) like this : (f@g@h)(x) I don't know where it could be used, but there could be some fun. Then, there is the multiplication chaining, but that belongs clearly to some other discussion, because that's getting close to lazy evaluation with underlying operation optimization. Indeed, why stop at just optimizating just the multiplication ?For this kind of expression-level optim, there is clearly no standard solution : numexpr, theano, ... ? (not familiar with this topic) So +1 for a plain and simple left associativity. (for weak or same, I don't think I understood all the aspects, but I feel that "same" is also the simplest choice) best, Pierre