-- -*- M2-comint -*- hash: 12166063486628630340

i1 : M = matroid({a,b,c,d},{{a,b},{a,c}})

o1 = a "matroid" of rank 2 on 4 elements

o1 : Matroid

i2 : for s in subsets M_* do print(toString s | " has closure " | toString closure_M s)
{} has closure {3}
{a} has closure {0, 3}
{b} has closure {1, 2, 3}
{a, b} has closure {0, 1, 2, 3}
{c} has closure {1, 2, 3}
{a, c} has closure {0, 1, 2, 3}
{b, c} has closure {1, 2, 3}
{a, b, c} has closure {0, 1, 2, 3}
{d} has closure {3}
{a, d} has closure {0, 3}
{b, d} has closure {1, 2, 3}
{a, b, d} has closure {0, 1, 2, 3}
{c, d} has closure {1, 2, 3}
{a, c, d} has closure {0, 1, 2, 3}
{b, c, d} has closure {1, 2, 3}
{a, b, c, d} has closure {0, 1, 2, 3}

i3 : F = flats M

o3 = {set {3}, set {1, 2, 3}, set {0, 3}, set {0, 1, 2, 3}}

o3 : List

i4 : all(F, f -> closure_M f === f)

o4 = true

i5 : 
