/// <summary>
/// Add a new edge with vertexs a and b to the truss.
/// </summary>
/// <param name="a"></param>
/// <param name="b"></param>
public void LinkJoints(char a, char b)
{
int posA = a - 'a';
int posB = b - 'a';
if (posA > joints.Count || posB > joints.Count || posA == posB)
{
throw new Exception($"Joint '{a}' or joint '{b}' does not exist, " +
$"or illegal connection of joints detected");
}
model.AddEdge(joints[posA], joints[posB]);
}
