colon -- colon of a (truncated) dual space

• Usage:

  Dg = colon(D,g)

  DJ = colon(D,J)

• Inputs:
  • D, an instance of the type DualSpace
  • g, a ring element
  • J, an ideal
• Optional inputs:
  • Tolerance => ..., default value .000001
• Outputs:
  • an instance of the type DualSpace, Dg, DJ