#11549: Arithmetic with symbolic vectors always creates a new
FreeModuleElement_generic_dense
-------------------------+--------------------------------------------------
Reporter: jvkersch | Owner: burcin
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.7.2
Component: symbolics | Keywords: vector, symbolic, arithmetic
Work_issues: | Upstream: N/A
Reviewer: David Roe | Author: Joris Vankerschaver, Jeroen Demeyer
Merged: | Dependencies:
-------------------------+--------------------------------------------------
Changes (by newvalueoldvalue):
* status: positive_review => needs_work
* author: => Joris Vankerschaver, Jeroen Demeyer
Old description:
> Arithmetic with symbolic vectors (addition, scalar multiplication)
> produces an instance of `FreeModuleElement_generic_dense` instead of a
> new symbolic vector:
>
> {{{
> sage: v = vector(SR, [1])
> sage: w = vector(SR, [x])
> sage: type(v)
> <class 'sage.modules.vector_symbolic_dense.Vector_symbolic_dense'>
> sage: type(w)
> <class 'sage.modules.vector_symbolic_dense.Vector_symbolic_dense'>
> sage: type(v + w)
> <type 'sage.modules.free_module_element.FreeModuleElement_generic_dense'>
> }}}
>
> As David Roe pointed out, the problem is due to the constructor in
> `FreeModuleElement_generic_dense` hard-coding the class, so that
> arithmetic operations with symbolic vectors ends up being a
> `FreeModuleElement_generic_dense` rather than an instance of
> `Vector_symbolic_dense`.
>
> See the discussion at https://groups.google.com/group/sage-
> devel/browse_thread/thread/b20559a111041c3b
New description:
Arithmetic with symbolic vectors (addition, scalar multiplication)
produces an instance of `FreeModuleElement_generic_dense` instead of a new
symbolic vector:
{{{
sage: v = vector(SR, [1])
sage: w = vector(SR, [x])
sage: type(v)
<class 'sage.modules.vector_symbolic_dense.Vector_symbolic_dense'>
sage: type(w)
<class 'sage.modules.vector_symbolic_dense.Vector_symbolic_dense'>
sage: type(v + w)
<type 'sage.modules.free_module_element.FreeModuleElement_generic_dense'>
}}}
As David Roe pointed out, the problem is due to the constructor in
`FreeModuleElement_generic_dense` hard-coding the class, so that
arithmetic operations with symbolic vectors ends up being a
`FreeModuleElement_generic_dense` rather than an instance of
`Vector_symbolic_dense`.
See the discussion at https://groups.google.com/group/sage-
devel/browse_thread/thread/b20559a111041c3b
Apply [attachment:trac_11549_symbolic_vector_arithmetic.patch] and
[attachment:11549_doc.patch]
--
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11549#comment:4>
Sage <http://www.sagemath.org>
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