Opened 9 years ago

Closed 9 years ago

#8502 closed defect (fixed)

evaluating multivariate polynomials yields non-constant

Reported by: cremona Owned by: AlexGhitza
Priority: major Milestone: sage-4.4
Component: algebra Keywords: polynomial evaluation
Cc: wuthrich, malb Merged in: sage-4.4.alpha0
Authors: John Cremona Reviewers: Alex Ghitza
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description

The following behaviour does not agree with the documentation for the {{{call}} function on multivariable polynomials, which states that (as one would expect and hope) the result should lie in the constant field:

sage: K.<t> = NumberField(x^2+47)
sage: R.<X,Y,Z> = K[]
sage: f = X+Y+Z
sage: a = f(t,t,t)
sage: a.parent()
Multivariate Polynomial Ring in X, Y, Z over Number Field in t with defining polynomial x^2 + 47

It is also inconsistent:

sage: R.<X,Y,Z> = QQ[]
sage: f = X+Y+Z
sage: a = f(2,3,4)
sage: a.parent()
Rational Field

This causes strange bugs -- see #8498 for an example.

Attachments (1)

trac_8502-mpoly.patch (1.9 KB) - added by cremona 9 years ago.
Applies to 4.3.5

Download all attachments as: .zip

Change History (5)

comment:1 Changed 9 years ago by cremona

  • Authors set to John Cremona
  • Cc malb added

Bug fixed: I added tests for when the resulting value is either 0, or a nonzero constant, in which case an element of the base ring is returned. Otherwise an element of the parent is returned (so you can still evaluate f(x+y,y) and similar.)

Patch up as soon as testing is finished.

malb: I'm CC-ing you as the past person to work on this file.

Changed 9 years ago by cremona

Applies to 4.3.5

comment:2 Changed 9 years ago by cremona

  • Status changed from new to needs_review

comment:3 Changed 9 years ago by AlexGhitza

  • Reviewers set to Alex Ghitza
  • Status changed from needs_review to positive_review

Looks good.

comment:4 Changed 9 years ago by jhpalmieri

  • Merged in set to sage-4.4.alpha0
  • Resolution set to fixed
  • Status changed from positive_review to closed

Merged "trac_8502-mpoly.patch" in 4.4.alpha0.

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