#18360: handle mutable objects better in symbolic evaluation
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Reporter: rws | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.7
Component: symbolics | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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In examples like this:
{{{
sage: f(x)=matrix()
sage: bool(f(x)-f(x)==0)
...
TypeError: mutable matrices are unhashable
}}}
the `f(x)` is expanded into a mutable matrix, but this prevents evaluation
because Pynac is called by `Expression._sub_` and wants to do hashes on
the matrix for comparison reasons. However, for the purpose of subtraction
dealing with a mutable matrix is completely unnecessary. So a solution
would be to turn mutable objects immutable before doing arithmetics in
`Expression` or in Pynac.
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Ticket URL: <http://trac.sagemath.org/ticket/18360>
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