#6482: [with patch, needs work] multivariate polynomial substitution has a
design
flaw
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Reporter: was | Owner: malb
Type: defect | Status: new
Priority: critical | Milestone: sage-4.1.2
Component: commutative algebra | Keywords:
Reviewer: | Author:
Merged: |
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Comment(by jason):
To emphasize the point, here is the result after applying the patch:
{{{
sage: R.<x,y>=QQ[]
sage: g=x+y
sage: g.subs({x:x+1,y:x*y})
x*y + x + 1
sage: g.subs({y:x*y, x:x+1})
x*y + x + 1
}}}
Note that things are *not* in order in the second example.
I think this is probably hopeless as stated. If the substitutions were
given as a list of tuples, then you could depend on the order. In other
words, if you had something like {{{g.subs([(y,x*y), (x,x+1)])}}} then you
could say something about doing the substitutions in order. Or even if
you did something like {{{g.subs((y,x*y), (x,x+1))}}} you could do
something in order, since *args is a list that preserves the order of the
arguments.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/6482#comment:7>
Sage <http://sagemath.org/>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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