trim Ideal doesn't trim all the way

[mahrud]

From Nick Addington via Google groups:

I ran this code:

R = QQ[x,y,X,Y,Z, Degrees=>{1,1,0,0,0}]
I = ideal(y*X-x*Z,x*Y-y*Z,x^2,y^2,x*y,Z-1,X*Y-Z^2,X-1,Y-1)
trim I

The output was

ideal(Z-1,Y-1,X-1,x-y,y^2,x*y,x^2)

when I would have expected

ideal(Z-1,Y-1,X-1,x-y,y^2)

Bizarrely, if I run

J = ideal(Z-1,Y-1,X-1,x-y,y^2,x*y,x^2)
trim J

then I do get the expected output.

Is this a bug, or should I tweak my input somehow?

I believe this is a bug, both in the graded and non-graded case:

i1 : R = QQ[x,y,X,Y,Z];

i2 : I = ideal(y*X-x*Z,x*Y-y*Z,x^2,y^2,x*y,Z-1,X*Y-Z^2,X-1,Y-1);

i3 : trim oo

                                         2        2
o3 = ideal (Z - 1, Y - 1, X - 1, x - y, y , x*y, x )

i4 : trim oo

                                         2
o4 = ideal (Z - 1, Y - 1, X - 1, x - y, y )

i5 : isHomogeneous  I

o5 = false

i6 : R = QQ[x,y,X,Y,Z, Degrees=>{1,1,0,0,0}];

i7 : I = ideal(y*X-x*Z,x*Y-y*Z,x^2,y^2,x*y,Z-1,X*Y-Z^2,X-1,Y-1);

i8 : trim oo

                                         2        2
o8 = ideal (Z - 1, Y - 1, X - 1, x - y, y , x*y, x )

i9 : trim oo

                                         2
o9 = ideal (Z - 1, Y - 1, X - 1, x - y, y )

i10 : isHomogeneous I

o10 = true

[mahrud]

Related: #1273