#13764: CartesianProduct with generators -> silent wrong answer
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Reporter: vbraun | Owner: sage-combinat
Type: defect | Status: needs_info
Priority: major | Milestone: sage-5.6
Component: combinatorics | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Volker Braun | Merged in:
Dependencies: | Stopgaps:
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Changes (by ncohen):
* status: new => needs_info
Comment:
Hellooooooo !!
Well, same question as the one asked on sage-devel : why shouldn't we
build the list of each iterator ? If the list is infinite then the code
will not terminate, but of course the user asked for it, and if we do make
lists from generators we store a quantity of information which is
(expectedly) small compared to the output ?
Err... Actually, if the function does not return a list but only "yields"
the elements one at a time, what we store could actually be much, much
more than what we should.
Hence, what about doing this :
* If we are given two lists, just do the job without problems
* If we are given iterators, convert them to lists first then do the job ?
With a `.. NOTE::` in the method's documentation, saying exactly that.
This way we never use more than what we actually need to use.
Nathann
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13764#comment:1>
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