Strange Polynomial substitution problem

[sagetrac-jbmohler]

I made a stupid error plugging a list into a polynomial, but it uncovered this very strange bug:

sage: R.<x,y,z,u,v,w>=ZZ[]
sage: P.<a>=ZZ[]
sage: e=[x^2,y^3]
sage: f=6*a^4
sage: f(x)
6*x^4
sage: f(e)
Exception exceptions.TypeError: "can't multiply sequence by non-int of type 'list'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand type(s) for *: 'NoneType' and 'NoneType'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand parent(s) for '*': 'Integer Ring' and '<type 'NoneType'>'" in 'sage.rings.polynomial.polynomial_compiled.mul_pd.eval' ignored
sage: f(x)
Exception exceptions.TypeError: "can't multiply sequence by non-int of type 'list'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand type(s) for *: 'NoneType' and 'NoneType'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand parent(s) for '*': 'Integer Ring' and '<type 'NoneType'>'" in 'sage.rings.polynomial.polynomial_compiled.mul_pd.eval' ignored

Notice that the plugging in the list seemed to ruin the polynomial good and proper.

Component: basic arithmetic

Issue created by migration from https://trac.sagemath.org/ticket/2360

[sagetrac-jbmohler]

comment:2

Ah, it's even easier. No second mpoly ring required!

sage: P.<a>=ZZ[]
sage: f=6*a^4
sage: f(1)
6
sage: f([1,2,3])
Exception exceptions.TypeError: "can't multiply sequence by non-int of type 'list'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand type(s) for *: 'NoneType' and 'NoneType'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand parent(s) for '*': 'Integer Ring' and '<type 'NoneType'>'" in 'sage.rings.polynomial.polynomial_compiled.mul_pd.eval' ignored
sage: f(1)  #  WHAT HAPPENED -- this worked before.
Exception exceptions.TypeError: "can't multiply sequence by non-int of type 'list'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand type(s) for *: 'NoneType' and 'NoneType'" in 'sage.rings.polynomial.polynomial_compiled.sqr_pd.eval' ignored
Exception exceptions.TypeError: "unsupported operand parent(s) for '*': 'Integer Ring' and '<type 'NoneType'>'" in 'sage.rings.polynomial.polynomial_compiled.mul_pd.eval' ignored

[malb]

comment:3

The attached patch fixes the issue. Credit goes to Tom Boothby too.

[robertwb]

comment:4

The patch fixes the issue, but I'd rather have the original error about multiplying lists propagate up instead of a generic "RuntimeError: Polynomial evaluation error in val()!"

[malb]

Attachment: trac_2360_fix.patch.gz

[malb]

comment:5

I updated the patch.

[robertwb]

comment:6

OK, that looks good.

[sagetrac-mabshoff]

comment:7

Merged in Sage 3.3.alpha2.

Cheers,

Michael