Evaluate this Data or TestData formula only once per date and return this value for any stock that references the item
Notes
This is most applicable to something like Extern($SPY, C > MA(C,200)) where the result will be the same for all symbols.
Prior to release 2.0.26.1 RealTest would nevertheless evaluate that same formula redundantly for every date of every symbol, and waste memory storing all these redundant values.
For this specific example RealTest now automatically applies #OnePerDate even if not specified.
Add this tag explicitly at the start of any formula to enforce this behavior.
Add both #OnePerDate and #OnePerSym to calculate and store only a single value for all bars of all stocks (this is done automatically for constants and constant expressions).
