Wrong substitution implementation for fraction fields

[novoselt]

I am getting this in 4.1.1 and find it really frustrating (especially since it took me several hours to catch):

sage: QQ["x", "y"].inject_variables()
Defining x, y
sage: e1 = x^2*y^3 - x^2*y - x*y
sage: e2 = e1.parent().fraction_field()(e1)
sage: print e2
x^2*y^3 - x^2*y - x*y
sage: print e2.subs(y=SR("s"))
x^2*s^3 - (x^2 - x)*s

The last line is wrong!

CC: @williamstein

Component: symbolics

Issue created by migration from https://trac.sagemath.org/ticket/7150

[sagetrac-fwclarke]

comment:1

But in 4.1.2.rc0:

sage: QQ["x", "y"].inject_variables()
Defining x, y
sage: e1 = x^2*y^3 - x^2*y - x*y
sage: e2 = e1.parent().fraction_field()(e1)
sage: print e2
x^2*y^3 - x^2*y - x*y
sage: print e2.subs(y=SR("s"))
s^3*x^2 - s*x^2 - s*x

So the problem may already have been solved.

[jasongrout]

comment:3

This may need to be closed with 4.1.2.

[mwhansen]

comment:4

Yep, I think we can close this.