#16721: symbolic gcd()
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps: todo
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Comment (by kcrisman):
{{{
<type 'sage.rings.integer.Integer'>
TESTS:
The following shows that indeed coercion takes place before computing
the gcd. This behaviour was introduced in trac ticket #10771::
sage: R.<x>=QQ[]
sage: S.<x>=ZZ[]
sage: p = S.random_element()
sage: q = R.random_element()
sage: parent(gcd(1/p,q))
Fraction Field of Univariate Polynomial Ring in x over Rational
Field
sage: parent(gcd([1/p,q]))
Fraction Field of Univariate Polynomial Ring in x over Rational
Field
}}}
and indeed
{{{
sage: parent(gcd(x,1))
Symbolic Ring
}}}
So in the symbolic ring this IS the gcd. Hmm. And if you think of this
as a polynomial, it makes sense.
So I'm not sure what to say here. The `4` might be a red herring in this
case, because we consider `SR` or whatever as more about polynomials over
a field, so the gcd is automatically one - maybe? Also check out
`x.gcd??`. Just raising questions about what the "right" thing to do is.
{{{
Make sure we try QQ and not merely ZZ (:trac:`13014`)::
sage: bool(gcd(2/5, 3/7) == gcd(SR(2/5), SR(3/7)))
True
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/16721#comment:5>
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