Am 29.05.2012 07:10, schrieb Aaron Meurer:
_hashable_content generally contains other Basic objects. So what I really want is the "fully denested" _hashable_content, where each Basic object is recursively replaced with its _hashable_content. I've no idea how expensive that would be to compute.
The behavior will be quadratic with number of levels of sets. This could start to impact us on deeply nested expressions - not with anything a human would enter, but if somebody wants to use SymPy from a script, this might be different. (I'm talking of thousands of nesting levels.) One way to set that might be to simplify x+0+0+...+0 (1000 terms, then retry with 100,000 ;-) ).
The downside of caching is that each mutator must invalidate the cached hash. (Unless mutators are disallowed once an object is entered into a dict. Or the mutable objects are really copy-on-write ones. I don't know whether any of these paths is available already, or feasible if unavailable - we're deep into Systems Programming Land here.)
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