complement(Face) -- Compute the complement face of a simplex.

i1 : R=QQ[x_0..x_4]

o1 = R

o1 : PolynomialRing

i2 : C=simplex R

o2 = 4: x x x x x  
         0 1 2 3 4

o2 : complex of dim 4 embedded in dim 4 (printing facets)
     equidimensional, simplicial, F-vector {1, 5, 10, 10, 5, 1}, Euler = 0

i3 : bC=boundaryOfPolytope C

o3 = 3: x x x x  x x x x  x x x x  x x x x  x x x x  
         0 1 2 3  0 1 2 4  0 1 3 4  0 2 3 4  1 2 3 4

o3 : complex of dim 3 embedded in dim 4 (printing facets)
     equidimensional, simplicial, F-vector {1, 5, 10, 10, 5, 0}, Euler = -1

i4 : F=bC.fc_2_0

o4 = x x x
      0 1 2

o4 : face with 3 vertices

i5 : complement F

o5 = x x
      3 4

o5 : face with 2 vertices