-- -*- M2-comint -*- {* hash: -725794466 *}

i1 : A := typeA(3)

o1 = {x  - x , x  - x , x  - x , x  - x , x  - x , x  - x }
       1    2   1    3   1    4   2    3   2    4   3    4

o1 : Hyperplane Arrangement 

i2 : L := flats(2,A)

o2 = {{0, 1, 3}, {0, 2, 4}, {0, 5}, {1, 4}, {1, 2, 5}, {2, 3}, {3, 4, 5}}

o2 : List

i3 : A' := restriction first L

o3 = {x  - x , x  - x , x  - x }
       3    4   3    4   3    4

o3 : Hyperplane Arrangement 

i4 : x := (ring A)_0  -- the subspace need not be in the arrangement

o4 = x
      1

o4 : QQ[x , x , x , x ]
         1   2   3   4

i5 : restriction(A,x)

o5 = {-x , -x , -x , x  - x , x  - x , x  - x }
        2    3    4   2    3   2    4   3    4

o5 : Hyperplane Arrangement 

i6 : trim A'

o6 = {x  - x }
       3    4

o6 : Hyperplane Arrangement 

i7 :