-- -*- M2-comint -*- hash: 5845958951555367850

i1 : R = QQ[x,y,z]

o1 = R

o1 : PolynomialRing

i2 : A = dual arrangement {x,y,x-y,z} -- the last element of this arrangement is 0

o2 = {-x , x , x , 0}
        1   1   1

o2 : Hyperplane Arrangement 

i3 : compress A

o3 = {-x , x , x }
        1   1   1

o3 : Hyperplane Arrangement 

i4 : 
