LaurentPolynomial_mpair.__init__ modifies input

[Etn40ff]

Creating mutlivariate Laurent polynomials from other mutlivariate Laurent polynomials sometimes fails.

sage: LQ = LaurentPolynomialRing(QQ, 'x0, x1, x2, y0, y1, y2, y3, y4, y5')
sage: LZ = LaurentPolynomialRing(ZZ, 'x0, x1, x2, y0, y1, y2, y3, y4, y5')
sage: LQ.inject_variables()
Defining x0, x1, x2, y0, y1, y2, y3, y4, y5
sage: x2^-1*y0*y1*y2*y3*y4*y5 + x1^-1*x2^-1*y0*y1*y3*y4 + x0^-1 in LZ
True
sage: x2^-1*y0*y1*y2*y3*y4*y5 + x1^-1*x2^-1*y0*y1*y3*y4 + x0^-1*x1^-1*y0*y3 + x0^-1 in LZ
Traceback (most recent call last):
...
AttributeError: 'tuple' object has no attribute 'esub'

Apparently this is due to the fact that LaurentPolynomial_mpair.__init__ changes the keys of the input dictionary.

CC: @dkrenn

Component: algebra

Author: Daniel Krenn

Branch/Commit: b56984c

Reviewer: Jeroen Demeyer

Issue created by migration from https://trac.sagemath.org/ticket/22398

[Etn40ff]

Commit: 500205f

[Etn40ff]

comment:1

Your patch seems to work.
Thanks

---

New commits:

ba66e9c	fix for loop whose changing its keys inside
500205f	Added trac reference

[Etn40ff]

Branch: public/ticket/22398

[sagetrac-git]

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

c930e8c

Trac #22398: minor rewrite to use tuple(...) instead of copy(...)

[sagetrac-git]

Changed commit from 500205f to c930e8c

[dkrenn]

Author: Daniel Krenn

[jdemeyer]

comment:5

The correct solution is to not modify the input data (instead of working around the fact that the input data is modified).

It would be good to add an explicit doctest showing that the input is not modified. Something like

sage: LQ.<x,y> = LaurentPolynomialRing(QQ)
sage: D = {(-1, 1): 1}
sage: type(D.keys()[0])
<type 'tuple'>
sage: LQ(D)
x^-1*y
sage: type(D.keys()[0])
<type 'tuple'>

[dkrenn]

comment:6

Replying to @jdemeyer:

The correct solution is to not modify the input data (instead of working around the fact that the input data is modified).

I completely agree. I'll adapt the patch during the day (once my 7.6.beta4 has recompiled again...).

[sagetrac-git]

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

a4e1504	Trac #22398: make `__init__` not modify its input
1ca887a	Trac #22398: simplify factoring out _mon
4a31db6	Trac #22398: doctest non-modifying input

[sagetrac-git]

Changed commit from c930e8c to 4a31db6

[dkrenn]

comment:8

Replying to @jdemeyer:

The correct solution is to not modify the input data (instead of working around the fact that the input data is modified).

Done. Needs_review (...and let's see what the patchbot says).

[jdemeyer]

comment:9

In the doctests, you can simplify code of the form

id_y = id(y)
id(x) == id_y

by

x is y

[sagetrac-git]

Changed commit from 4a31db6 to 1f2d7f4

[sagetrac-git]

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

1f2d7f4

Trac #22398: simplify id(...) = id(...) in doctest

[dkrenn]

comment:11

Replying to @jdemeyer:

In the doctests, you can simplify code of the form

id(x) == id(y)

by

x is y

Oh, indeed :) ...done.

[jdemeyer]

Reviewer: Jeroen Demeyer

[jdemeyer]

comment:12

If tests pass, you can set this to positive_review.

[sagetrac-git]

Changed commit from 1f2d7f4 to b56984c

[sagetrac-git]

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

b56984c

Trac #22398: py3: fix

[vbraun]

Changed branch from public/ticket/22398 to b56984c