"Source: Text/Incidence/Plane.text";
"Line: 870";
"Date: Fri Sep 26 12:10:10 2025";
"Main: Fri Sep 26 14:29:19 2025";
// original file: Text/Incidence/Plane.text, line: 870
// Example: H154E5 ()
print "Example: H154E5";
ei := GetEchoInput();
SetEchoInput(true);
A := FiniteAffinePlane(4);
VectorSpace(A);
Field(A);      
P := FiniteProjectivePlane< 7 | {1, 3, 5}, {1, 2, 7}, {1, 4, 6}, {2, 3, 6},
                           {2, 4, 5}, {3, 4, 7}, {5, 6, 7} >;
IP := IncidenceMatrix(P);
IP;
D := Dual(P);
D;
IncidenceMatrix(D) eq Transpose(IP);
assert $1;
SetEchoInput(ei);
