Implement QQbar^QQ as action #5574

burcin · 2009-03-20T10:09:12Z

This ticket implements powering in QQbar and AA by QQ exponents as an action.

This will fix the following two bugs:

Reported by Alex Raichev on sage-support:

sage: n = SR.var('n'); QQbar(2)^n
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-6-01e1c4db05c9> in <module>()
----> 1 n = SR.var('n'); QQbar(Integer(2))**n

/usr/local/src/sage-config/local/lib/python2.7/site-packages/sage/rings/qqbar.pyc in __pow__(self, e)
   4106         if self == self.parent().one():
   4107             return self.parent().one()
-> 4108         e = QQ._coerce_(e)
   4109         n = e.numerator()
   4110         d = e.denominator()

/usr/local/src/sage-config/src/sage/structure/parent_old.pyx in sage.structure.parent_old.Parent._coerce_ (build/cythonized/sage/structure/parent_old.c:5673)()
    227     def _coerce_(self, x):            # Call this from Python (do not override!)
    228         if self._element_constructor is not None:
--> 229             return self.coerce(x)
    230         check_old_coerce(self)
    231         return self._coerce_c(x)

/usr/local/src/sage-config/src/sage/structure/parent.pyx in sage.structure.parent.Parent.coerce (build/cythonized/sage/structure/parent.c:10829)()
   1157                 except Exception:
   1158                     _record_exception()
-> 1159             raise TypeError("no canonical coercion from %s to %s" % (parent(x), self))
   1160         else:
   1161             return (<map.Map>mor)._call_(x)

TypeError: no canonical coercion from Symbolic Ring to Rational Field

sage: QQbar(2)^1.0
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-aba7adf5dc93> in <module>()
----> 1 QQbar(Integer(2))**RealNumber('1.0')

/usr/local/src/sage-config/local/lib/python2.7/site-packages/sage/rings/qqbar.pyc in __pow__(self, e)
   4106         if self == self.parent().one():
   4107             return self.parent().one()
-> 4108         e = QQ._coerce_(e)
   4109         n = e.numerator()
   4110         d = e.denominator()

/usr/local/src/sage-config/src/sage/structure/parent_old.pyx in sage.structure.parent_old.Parent._coerce_ (build/cythonized/sage/structure/parent_old.c:5673)()
    227     def _coerce_(self, x):            # Call this from Python (do not override!)
    228         if self._element_constructor is not None:
--> 229             return self.coerce(x)
    230         check_old_coerce(self)
    231         return self._coerce_c(x)

/usr/local/src/sage-config/src/sage/structure/parent.pyx in sage.structure.parent.Parent.coerce (build/cythonized/sage/structure/parent.c:10829)()
   1157                 except Exception:
   1158                     _record_exception()
-> 1159             raise TypeError("no canonical coercion from %s to %s" % (parent(x), self))
   1160         else:
   1161             return (<map.Map>mor)._call_(x)

TypeError: no canonical coercion from Real Field with 53 bits of precision to Rational Field

CC: @videlec

Component: algebra

Author: Jeroen Demeyer

Branch/Commit: f65afd0

Reviewer: Vincent Delecroix

Issue created by migration from https://trac.sagemath.org/ticket/5574

The text was updated successfully, but these errors were encountered:

burcin · 2009-04-09T13:31:11Z

comment:1

From sage-support @freenode today:

<base3___> raising a matrix to a variable power fails with 
NotImplementedError: non-integral exponents not supported,
even if i do assume(n, 'integer')
<base3___> am i missing something or should i file this as a bug?
<burcin> base3___, it's a bug

rwst · 2015-10-19T13:58:56Z

comment:6

This is a general shortcoming of AlgebraicNumber.__pow__():

sage: (QQbar(2)^3)^1.
...
TypeError: no canonical coercion from Real Field with 53 bits of precision to Rational Field

jdemeyer · 2018-01-08T09:03:36Z

Dependencies: #24247

videlec · 2018-01-08T11:14:03Z

comment:10

Note that this is not a group action (because of the choice of an n-th root)

((-1)^(1/3))^2 != ((-1)^2)^(1/3).

Isn't that a requirement that g.(h.x) = (gh).x for an action in Sage?

jdemeyer · 2018-01-08T11:26:16Z

Changed dependencies from #24247 to #24247, #24490

jdemeyer · 2018-01-08T11:30:09Z

comment:12

Replying to @videlec:

Note that this is not a group action (because of the choice of an n-th root)
((-1)^(1/3))^2 != ((-1)^2)^(1/3).

So what? I don't plan to change any arithmetic, just the underlying implementation. Since we have an operation between 2 different parents (QQbar and QQ), an action is the right way to implement this.

Isn't that a requirement that g.(h.x) = (gh).x for an action in Sage?

Why should there be such a requirement? I see an action purely as a technical way to implement a certain operation.

sagetrac-git · 2018-01-09T10:53:33Z

Changed commit from 6b880d2 to 2591b72

jdemeyer · 2018-01-09T10:53:54Z

Changed dependencies from #24247, #24490 to #24247

jdemeyer · 2018-01-18T10:10:45Z

Changed dependencies from #24247 to none

sagetrac-git · 2018-01-18T10:11:31Z

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

`5bfd169`	`Implement QQbar^QQ as action`

sagetrac-git · 2018-01-18T10:11:31Z

Changed commit from 2591b72 to 5bfd169

jdemeyer · 2018-01-18T10:12:19Z

comment:23

Rebased to 8.2.beta3

jdemeyer · 2018-01-18T10:14:32Z

comment:24

This is a dependency for both #24256 and #24500, so it would be good to get this ticket done.

videlec · 2018-01-25T14:50:08Z

comment:25

Is that complient with Sage documentation?

EXAMPLES in ``QQbar``::
...
EXAMPLES in ``AA``::
...

Why not

EXAMPLES:

powering in ``QQbar``::
...
powering in ``AA``::
...

videlec · 2018-01-25T14:54:17Z

comment:26

Timings look like it will be a bit slower. Before

sage: a = AA(5)
sage: %timeit a^(1/3)
1000 loops, best of 3: 327 µs per loop
sage: a = AA(8)
sage: %timeit a^(1/3)
100000 loops, best of 3: 7.78 µs per loop

After

sage: a = AA(5)
sage: %timeit a^(1/3)
1000 loops, best of 3: 369 µs per loop
sage: a = AA(8)
sage: %timeit a^(1/3)
100000 loops, best of 3: 9.64 µs per loop

jdemeyer · 2018-01-25T16:00:33Z

comment:27

Timings should improve in #24500 but I obviously cannot promise that it will be as fast as before.

jdemeyer · 2018-01-25T16:18:56Z

comment:28

Replying to @videlec:

Is that complient with Sage documentation?
EXAMPLES in ``QQbar``::
...
EXAMPLES in ``AA``::
...

There are some cases like that already in Sage. I don't see the problem, but if you insist, then I will change it.

videlec · 2018-01-25T16:22:17Z

comment:29

Replying to @jdemeyer:

Replying to @videlec:
Is that complient with Sage documentation?
EXAMPLES in ``QQbar``::
...
EXAMPLES in ``AA``::
...
There are some cases like that already in Sage. I don't see the problem, but if you insist, then I will change it.

My reference is http://doc.sagemath.org/html/en/developer/coding_basics.html#documentation-strings (and not the rest of Sage).

jdemeyer · 2018-01-25T17:22:08Z

comment:30

I don't see anything in the docs saying that an EXAMPLES block should start exactly with the line EXAMPLES::

jdemeyer · 2018-01-25T17:23:00Z

comment:31

This is different from Sphinx blocks like .. WARNING:: because those are handled specially. But there is nothing special about EXAMPLES.

videlec · 2018-01-25T23:30:46Z

comment:32

Replying to @jdemeyer:

This is different from Sphinx blocks like .. WARNING:: because those are handled specially. But there is nothing special about EXAMPLES.

TESTS is also handled specially (hided in the doc). And EXAMPLES might in the future (e.g. interactive execution in Jupyter).

jdemeyer · 2018-01-26T08:47:10Z

comment:33

Replying to @videlec:

And EXAMPLES might in the future (e.g. interactive execution in Jupyter).

That would be a bad idea. Executable commands should be limited to the EXAMPLES block.

And if some software really wants to treat EXAMPLES blocks specially, it should still recognize EXAMPLES in ``QQbar`` as EXAMPLES block.

Anyway, if you really want me to change it, just say so.

videlec · 2018-01-26T09:03:40Z

comment:34

Replying to @jdemeyer:

Replying to @videlec:

And EXAMPLES might in the future (e.g. interactive execution in Jupyter).

That would be a bad idea. Executable commands should be limited to the EXAMPLES block.

And if some software really wants to treat EXAMPLES blocks specially, it should still recognize EXAMPLES in ``QQbar`` as EXAMPLES block.

Anyway, if you really want me to change it, just say so.

Please do.

sagetrac-git · 2018-01-29T16:07:42Z

Changed commit from 5bfd169 to f65afd0

sagetrac-git · 2018-01-29T16:07:42Z

Branch pushed to git repo; I updated commit sha1. New commits:

`f65afd0`	`Change docstring formatting`

videlec · 2018-01-29T22:17:38Z

Reviewer: Vincent Delecroix

vbraun · 2018-02-02T12:06:18Z

Changed branch from u/jdemeyer/implement_qqbar_qq_as_action to f65afd0

burcin added this to the sage-5.11 milestone Mar 20, 2009

burcin added c: symbolics labels Mar 20, 2009

jdemeyer modified the milestones: sage-5.11, sage-5.12 Aug 13, 2013

sagetrac-vbraun-spam mannequin modified the milestones: sage-6.1, sage-6.2 Jan 30, 2014

sagetrac-vbraun-spam mannequin modified the milestones: sage-6.2, sage-6.3 May 6, 2014

sagetrac-vbraun-spam mannequin modified the milestones: sage-6.3, sage-6.4 Aug 10, 2014

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rwst modified the milestones: sage-6.4, sage-6.10 Oct 19, 2015

rwst changed the title ~~taking symbolic powers should coerce objects to symbolic expressions~~ AlgebraicNumber.__pow__() does only rational exponents Oct 19, 2015

rwst added c: algebra and removed c: symbolics labels Oct 19, 2015

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jdemeyer changed the title ~~AlgebraicNumber.__pow__() does only rational exponents~~ Fix AlgebraicNumber.__pow__ Jan 8, 2018

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jdemeyer changed the title ~~Fix AlgebraicNumber.__pow__~~ Implement QQbar^QQ as action Jan 8, 2018

jdemeyer modified the milestones: sage-6.10, sage-8.2 Jan 8, 2018

jdemeyer added s: needs review and removed s: needs work labels Jan 9, 2018

videlec added s: positive review and removed s: needs review labels Jan 29, 2018

vbraun removed the s: positive review label Feb 2, 2018

vbraun closed this as completed in 5473d30 Feb 2, 2018

videlec mentioned this issue Jun 1, 2021

Cleanup and speedup in QQbar #18333

Open

jdemeyer mentioned this issue Dec 29, 2022

Do not allow QQbar(1) ^ anything #24490

Open

tscrim mentioned this issue Feb 8, 2018

Implement actions using _act_ instead of _call_ #24500

Closed

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Implement QQbar^QQ as action #5574

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Implement QQbar^QQ as action #5574

Implement QQbar^QQ as action #5574

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