On 17/09/15 06:53, Simon King wrote:
Hi!
On 2015-09-17, Jeroen Demeyer <jdeme...@cage.ugent.be> wrote:
On 2015-09-16 16:43, Jean-Pierre Flori wrote:
Hi,
I guess one of the issue is that there is no canonical map between two
different representations of the same finite field (so no coercion).
The question is really: is the map between representations of the same
finite field, which differ only in variable name, "canonical"?
I think that it is in the same way canonical as we have a
name-preserving map between polynomial rings.
The real problem here is that *conversion* gives rise to an error
that mentions *coercion*.
sage: K.<x> = GF(25)
sage: L.<y> = GF(25)
sage: K(y)
Traceback (most recent call last):
...
TypeError: unable to coerce from a finite field other than the prime subfield
That's clearly a bug. Conversion should work, even if it isn't canonical
and thus doesn't qualify as coercion!
Is there no ticket for it already? I think I have seen that issue
before.
+1
The behavior should be similar to
sage: Rx.<x> = ZZ[]
sage: Ry.<y> = ZZ[]
sage: Rx(3*y**2 + 1)
3*x^2 + 1
sage: x+y
Traceback (most recent call last):
...
TypeError: unsupported operand parent(s) for '+': 'Univariate Polynomial
Ring in x over Integer Ring' and 'Univariate Polynomial Ring in y over
Integer Ring'
Vincent
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