forced coercion vs. automatic coercion

[nbruin]

This should give similar results, but it is inconsistent:

P1.<x>=QQ[]
L=P1.fraction_field()
x=L(x)
P2.<y>=P1[]

f=x+y

P3.<x,y>=QQ[]

P3(f)

0*P3.0+f

---

Apply

1. attachment: trac813_univariate_coerce_from_multivariate.patch
2. attachment: trac_813_review.patch

to the Sage library repository.

Depends on #9944

Component: coercion

Author: Simon King

Reviewer: Julian Rueth

Merged: sage-4.7.2.alpha3

Issue created by migration from https://trac.sagemath.org/ticket/813

[roed314]

comment:3

I will work on this once Robert has added rdef'd functions to Sage (that way I don't have to redo the changes once this occurs)

[mwhansen]

comment:5

This now gives a TypeError when doing the last arithmetic:

TypeError: unsupported operand parent(s) for '+': 'Multivariate Polynomial Ring in x, y over Rational Field' and 'Univariate Polynomial Ring in y over Fraction Field of Univariate Polynomial Ring in x over Rational Field'