Despite the potential speed increase (I've implemented some and it can be considerable), SAGE has avoided almost all use of inplace operators due to the fact that elements are supposed to be immutable, despite the fact that one does not really need the "old" result anymore. For example, if I type x^5 - 3*x + 1, the subexpressions (x^5), (3*x), and (x^5-3*x) are all created and then discarded. This also shows up in places like the operation sum() which doesn't return any of its intermediate results, or loops that increment variables in certain ways. The worry is that perhaps somewhere something else is holding onto a given variable, and we don't want to mess it up.
Just the other day, I realized that Python provides the perfect solution--by looking at the reference count of an object we can detect whether or not its safe to mutate it (i.e. nothing else is holding onto it but the current call). If it is safe to mutate, then do so, otherwise create and return a new object. I propose adding _iadd_c, _imul_c, etc. to the coercion hierarchy such that the default __iadd__/__add__ detects whether or not inplace operations are safe and calls the respective operation accordingly. One would have bold comments on functions that are not safe to call directly. The only caveat is that it might make it a tiny bit slower for types that do not define inplace operations, and it would take a slight (SAGE-specific and optional) tweak to Cython (specifically Cython local function variables have a refcount one less than expected due to their not being in any kind of a python "scope" container, so we would need an extra incref/decref them when performing arithmetic on them). - Robert --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
