isFace -- Test whether a face is a face of a given complex.

i1 : K=QQ;

i2 : R=K[x_1..x_5];

i3 : C=idealToComplex ideal (x_1*x_2,x_3*x_4*x_5)

o3 = {x  x  x  , x  x  x  , x  x  x  , x  x  x  , x  x  x  , x  x  x  }
       1  3  4    2  3  4    2  4  5    2  3  5    1  4  5    1  3  5

o3 : complex with 6 facets on the vertices x  x  x  x  x  
                                            1  2  3  4  5

i4 : F1=face {x_1,x_2}

o4 = x  x  
      1  2

o4 : face with 2 vertices

i5 : F2=face {x_1,x_3}

o5 = x  x  
      1  3

o5 : face with 2 vertices

i6 : isFace(F1,C)

o6 = false

i7 : isFace(F2,C)

o7 = true