The restriction of M to S, M | S, has ground set S and independent sets equal to the independent sets of M contained in S.
i1 : M = matroid({a,b,c,d},{{a,b},{a,c}}) o1 = a matroid of rank 2 on 4 elements o1 : Matroid |
i2 : N = M | {a,b,d} o2 = a matroid of rank 2 on 3 elements o2 : Matroid |
i3 : peek N o3 = Matroid{bases => {set {0, 1}} } cache => CacheTable{...2...} groundSet => set {0, 1, 2} rank => 2 |
i4 : N == M | set{0,1,3} o4 = true |
The object restriction is a method function.