Ticket #4246 (assigned defect)

Opened 2 months ago

Last modified 4 days ago

[with patch, needs review] bug in coercing symbolic expressions to polynomial rings

Reported by: AlexGhitza Assigned to: AlexGhitza (accepted)
Priority: major Milestone: sage-3.2.2
Component: calculus Keywords:
Cc: robertwb

Description

This was reported by William Stein at #4106:

I did notice this unfortunate property of the _polynomial_ function that is used to implement this patch, namely it does something dumb when given x+y as input: 

  sage: var('x')
  x
  sage: var('y')
  y
  sage: S = PolynomialRing(Integers(4),1,'x')
  sage: S(x+y)
  2*x
  sage: (x+y)._polynomial_(S)
  2*x

I think in this case it should raise a TypeError.

Attachments

trac4246-coerce_symbolic_into_polyrings.patch (2.1 kB) - added by AlexGhitza on 10/05/2008 02:48:31 PM.
trac4246-coerce_symbolic_into_polyrings_1.patch (1.0 kB) - added by AlexGhitza on 11/28/2008 11:27:37 PM.

Change History

10/05/2008 02:48:31 PM changed by AlexGhitza

  • attachment trac4246-coerce_symbolic_into_polyrings.patch added.

10/05/2008 02:49:01 PM changed by AlexGhitza

  • status changed from new to assigned.
  • summary changed from bug in coercing symbolic expressions to polynomial rings to [with patch, needs review] bug in coercing symbolic expressions to polynomial rings.

10/05/2008 04:23:13 PM changed by mhansen

  • summary changed from [with patch, needs review] bug in coercing symbolic expressions to polynomial rings to [with patch, positive review] bug in coercing symbolic expressions to polynomial rings.

Looks good to me.

10/07/2008 01:59:20 PM changed by mabshoff

  • cc set to robertwb.
  • summary changed from [with patch, positive review] bug in coercing symbolic expressions to polynomial rings to [with patch, needs work] bug in coercing symbolic expressions to polynomial rings.

This patch breaks two doctests in coerce_maps.pyx: 

mabshoff@sage:/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3$ ./sage -t -long devel/sage/sage/structure/coerce_maps.pyx
sage -t -long devel/sage/sage/structure/coerce_maps.pyx     
**********************************************************************
File "/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3/tmp/coerce_maps.py", line 110:
    sage: mor(x^2/4+1)
Exception raised:
    Traceback (most recent call last):
      File "/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3/local/lib/python2.5/doctest.py", line 1228, in __run
        compileflags, 1) in test.globs
      File "<doctest __main__.example_3[4]>", line 1, in <module>
        mor(x**Integer(2)/Integer(4)+Integer(1))###line 110:
    sage: mor(x^2/4+1)
      File "map.pyx", line 133, in sage.categories.map.Map.__call__ (sage/categories/map.c:2755)
      File "coerce_maps.pyx", line 146, in sage.structure.coerce_maps.NamedConvertMap._call_ (sage/structure/coerce_maps.c:3348)
      File "/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3/local/lib/python2.5/site-packages/sage/calculus/calculus.py", line 1886, in _polynomial_
        raise TypeError, "%s is not a variable of %s" %(v, R)
    TypeError: x is not a variable of Univariate Polynomial Ring in t over Rational Field
**********************************************************************
File "/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3/tmp/coerce_maps.py", line 113:
    sage: mor(x^2/4+1)
Exception raised:
    Traceback (most recent call last):
      File "/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3/local/lib/python2.5/doctest.py", line 1228, in __run
        compileflags, 1) in test.globs
      File "<doctest __main__.example_3[6]>", line 1, in <module>
        mor(x**Integer(2)/Integer(4)+Integer(1))###line 113:
    sage: mor(x^2/4+1)
      File "map.pyx", line 133, in sage.categories.map.Map.__call__ (sage/categories/map.c:2755)
      File "coerce_maps.pyx", line 146, in sage.structure.coerce_maps.NamedConvertMap._call_ (sage/structure/coerce_maps.c:3348)
      File "/scratch/mabshoff/release-cycle/sage-3.1.3.alpha3/local/lib/python2.5/site-packages/sage/calculus/calculus.py", line 1886, in _polynomial_
        raise TypeError, "%s is not a variable of %s" %(v, R)
    TypeError: x is not a variable of Power Series Ring in t over Finite Field of size 7
**********************************************************************

Since this is coercion related I am adding RobertWB to the CC.

Cheers,

Michael

11/28/2008 11:27:37 PM changed by AlexGhitza

  • attachment trac4246-coerce_symbolic_into_polyrings_1.patch added.

11/28/2008 11:29:04 PM changed by AlexGhitza

  • summary changed from [with patch, needs work] bug in coercing symbolic expressions to polynomial rings to [with patch, needs review] bug in coercing symbolic expressions to polynomial rings.

I added a small patch that changes the two failing doctests slightly so that they pass now. I thought about the behaviour a bit and it seems sensible to me, but Robert should feel free to defend the original doctests if necessary.