#5679: fix a bug in solve and polynomial generators
------------------------+---------------------------------------------------
Reporter: was | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-4.7
Component: calculus | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
------------------------+---------------------------------------------------
Changes (by kcrisman):
* upstream: => N/A
Comment:
In Sage 4.6.2:
{{[
sage: f = symbolic_expression(x0) == 0
sage: f.solve(x0)
---------------------------------------------------------------------------
TypeError: x0 is not a valid variable.
sage: f.solve(symbolic_expression(x0))
[x0 == 0]
}}}
This is because
{{{
if not isinstance(x, Expression):
raise TypeError, "%s is not a valid variable."%x
}}}
So I guess one could check whether SR(x) is a symbol?
{{{
sage: symbolic_expression(x0)._is_symbol()
True
}}}
Incidentally, we never get to the `args[0]` because you are solving a
single expression, so it goes to `ex.solve(*args)`. So maybe we should
check for that... But in any case the syntax is now
{{{
sage: solve([symbolic_expression(x0) == 0, 0==0], [x0, x1, x2])
---------------------------------------------------------------------------
TypeError: x0 is not a valid variable.
}}}
which ''does'' raise the error in question.
But
{{{
sage: solve([symbolic_expression(x0) == 0, 0==0], [SR(x0), SR(x1),
SR(x2)])
[[x0 == 0, x1 == r2, x2 == r1]]
}}}
Weirdly,
{{{
sage: solve([symbolic_expression(x0) == 0], SR(x0), SR(x1), SR(x2))
([x0 == 0], [1])
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5679#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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