#19538: Fix LaurentPolynomialRing coercion issues
-------------------------+-------------------------------------------------
Reporter: | Owner:
etn40ff | Status: needs_review
Type: | Milestone: sage-6.10
defect | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
algebra | Work issues:
Keywords: | Commit:
Authors: | 76ac4339b195762106d406516400f8468de844ef
Salvatore Stella | Stopgaps:
Report Upstream: N/A |
Branch: |
u/etn40ff/19358 |
Dependencies: |
-------------------------+-------------------------------------------------
Description changed by etn40ff:
Old description:
> `LaurentPolynomialRing` has some issues when trying to compare elements
> from different rings:
>
> {{{
> sage: L = LaurentPolynomialRing(ZZ, 'x0,x1,x2,y0,y1,y2')
> sage: P = LaurentPolynomialRing(ZZ, 'y0,y1,y2')
> sage: P.inject_variables()
> Defining y0, y1, y2
> sage: y0 in L
> False
> }}}
>
> This patch should fix them. In the process it also changes this somewhat
> weird behaviour:
>
> {{{
> sage: L = LaurentPolynomialRing(ZZ, 'x', 4)
> sage: R = LaurentPolynomialRing(ZZ, 'x3,x2,t,s')
> sage: R.inject_variables()
> Defining x3, x2, t, s
> sage: L(x3)
> x0
> sage: L(t)
> x2
> }}}
>
> NOTE: This behaviour still survives in `PolynomialRing`
New description:
`LaurentPolynomialRing` has some issues when trying to compare elements
from different rings:
{{{
sage: L1 = LaurentPolynomialRing(ZZ, 'x0,x1,x2,y0,y1,y2')
sage: L2 = LaurentPolynomialRing(ZZ, 'y0,y1,y2')
sage: L2.gen(0) in L1
False
sage: L1(L2.gen(0))
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
...
TypeError: tuple key must have same length as ngens
}}}
The corresponding code for `PolynomialRing` yields
{{{
sage: P1 = PolynomialRing(ZZ, 'x0,x1,x2,y0,y1,y2')
sage: P2 = PolynomialRing(ZZ, 'y0,y1,y2')
sage: P2.gen(0) in P1
True
sage: P1(P2.gen(0))
y0
}}}
This patch should fix them. In the process it also changes this somewhat
weird behaviour:
{{{
sage: L = LaurentPolynomialRing(ZZ, 'x', 4)
sage: R = LaurentPolynomialRing(ZZ, 'x3,x2,t,s')
sage: R.inject_variables()
Defining x3, x2, t, s
sage: L(x3)
x0
sage: L(t)
x2
}}}
NOTE: This behaviour still survives in `PolynomialRing`
--
--
Ticket URL: <http://trac.sagemath.org/ticket/19538#comment:14>
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