#807: construction of function fields
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Reporter: nbruin | Owner: somebody
Type: defect | Status: new
Priority: major | Milestone: sage-5.8
Component: basic arithmetic | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by cremona):
Replying to [comment:6 tscrim]:
> I think the underlying problem is that the language syntax does not
truly support doing `QQ[]`, so when it is trying to parse
`QQ[].fraction_field()`, it first must evaluate `QQ[]` as a standalone
(thus the `SyntaxError`), in order to get the output object to find the
attribute `fraction_field()`.
>
> I don't know where/how the syntax `P.<x> = QQ[]` comes from/works (in
the preparser perhaps?), so perhaps we can use that, but I don't know if
that is easily done, safe, or even feasible. I'll do some looking around,
but I'm thinking this might not be doable considering the semantics of
python... Anyone else's thoughts?
{{{
sage: preparse("P.<x> = QQ[]")
"P = QQ['x']; (x,) = P._first_ngens(1)"
}}}
As I understand it, the . before the < triggers a python error which is
caught and then handled nicely.
>
> Best,[[BR]]
> Travis
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/807#comment:7>
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