Opened 12 years ago

# unhandled case in converting to polynomial ring

Reported by: Owned by: cwitty malb major sage-6.4 commutative algebra N/A

### Description

Normally, Sage tries to allow explicit conversions between arbitrary polynomial rings, if they share the same variable names.

Here's a case where that doesn't work:

```R.<a,b,c,d,e,f,x,y,z,t,s,r>=PolynomialRing(QQ,12,order='lex')
I=R.ideal(a^2+d^2-x,a*b+d*e-y,a*c+d*f-z,b^2+e^2-t,b*c+e*f-s,c*c+f*f-r)
j=I.groebner_basis()
R1.<x,y,z,t,s,r>=QQ[]
R2=FractionField(R1)
R3.<a,b,c,d,e,f>=R1.fraction_field()[]
R3(j[0])
```

For now, the workaround is:

``` sage_eval(str(j[0]), locals=locals())
```

but IMHO the original code should work.

### comment:1 Changed 8 years ago by jdemeyer

• Milestone changed from sage-5.11 to sage-5.12

### comment:2 Changed 7 years ago by vbraun_spam

• Milestone changed from sage-6.1 to sage-6.2

### comment:3 Changed 7 years ago by vbraun_spam

• Milestone changed from sage-6.2 to sage-6.3

### comment:4 Changed 7 years ago by vbraun_spam

• Milestone changed from sage-6.3 to sage-6.4

### comment:5 Changed 5 years ago by bruno

• Report Upstream set to N/A

A smaller example (minimal I hope ;-)):

```sage: R = QQ['a,b,x,y']
sage: S = Frac(QQ['x,y'])['a,b']
sage: p = R.gen(0) + R.gen(1) + R.gen(2)
sage: S(p)
Traceback (most recent call last):
...
TypeError: Could not find a mapping of the passed element to this ring.
```
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