#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 nbruin):
Replying to [comment:9 tscrim]:
Ah, I wasn't aware of the `FractionField` behaviour.
In a way, ignoring "names" would be good. Compare:
{{{
sage: preparse("R.<x>=QQ[t]")
'R = QQ[t]; (x,) = R._first_ngens(1)'
sage: preparse("R.<x>=PolynomialRing(QQ,'t')")
"R = PolynomialRing(QQ,'t', names=('x',)); (x,) = R._first_ngens(1)"
sage: preparse("R.<x>=PolynomialRing(QQ,names='t')")
"R = PolynomialRing(QQ,names='t', names=('x',)); (x,) = R._first_ngens(1)"
}}}
In the first and second cases, it is recognised that a print name supplied
by the LHS is superfluous, so it gets ignored (meaning: not inserted into
the RHS). In the third case, the preparser fails to recognize this (the
preparser will always have problems like that).
Given that print names are always superfluous for FractionField, ignoring
the names field would be the right thing. However, I think
`fraction_field` is not the proper place to do this and it would not solve
the issue of this ticket: In
{{{
P1.<t>=FractionField(QQ[])
}}}
or
{{{
P1.<t>=QQ[].fraction_field()
}}}
it's not just that a `names=('t',)` should not be injected into the
`fraction_field` call, it should be injected into the polynomial ring
constructor. Of course, for this case the solution is
{{{
sage: P1.<t>=FunctionField(QQ)
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/807#comment:12>
Sage <http://www.sagemath.org>
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