x[Time - n]
This is synonymous with the slice expression
x[@Time = Time - n].
The name IdentPred
The name IdentPred appears in the Analytica namespace as if it were a built-in system function. However, there is no function calling syntax for invoking this using the name IdentPred. As an Analytica user, you will seldom see this identifier unless you start poking around in the internals. Internally, the object named IdentPred is a placeholder for this operator, which gets invoked by the engine like other built-in functions to. You should never use the identifier IdentPred directly in your code.