Invalid

Description:	Return Invalid Value. This function always returns an invalid value.
Returns:	Invalid
Function Groups:	Logic Control,  Variable
Usage:	Script or steady state.
Related to:	Valid
Format:	Invalid()
Parameters:	None

Comments:

This function is useful to invalidate data that are found to be incorrect, or to disable statements or functions that will not execute with invalid parameters.

Examples:

x = Valid(Invalid());

This will set x to 0.

Another example of this function's usefulness follows:

Main [
  If !Valid(a);
  [ 
    a = Scale(Rand(), 0, 1, -1000, 1000); 
    ... 
  ] 
  If Valid(a);
  [ 
    ... 
    a = Invalid(); 
  ] 
]

By toggling between a valid and an invalid value, you can ensure that the two scripts in Main will take turns executing. It is not possible for a race condition to occur.