code: public Breakpoint clearBreakpoint(int bpno)
  	{
  		Breakpoint old = breakpoints.remove(bpno);
  
  		if (old != null)
  		{
  			PStm stmt = findStatement(old.location.getFile(), old.location.getStartLine());
  
  			if (stmt != null)
  			{
  				BreakpointManager.setBreakpoint(stmt, new Breakpoint(stmt.getLocation()));
  			} else
  			{
  				PExp exp = findExpression(old.location.getFile(), old.location.getStartLine());
  				assert exp != null : "Cannot locate old breakpoint?";
  				BreakpointManager.setBreakpoint(exp, new Breakpoint(exp.getLocation()));
  			}
  		}
  
  		return old; // null if not found
  	}
docs: Clear the breakpoint given by the number.
  
  @param bpno
  The breakpoint number to remove.
  @return The breakpoint object removed, or null.