[amibroker] Improper code behavior

["Rick Charon" <rickcharon@xxxxxxxxx>]

The following code doesn't work as expected. What am I missing? 
Thanks. (The buy flips once, then stays 1, even though Ref(posOpen, -
1) is 1. 

Filter = 1;

posOpen[0] = 0;

Buy = (Ref(posOpen, -1) == 0); 

posOpen = Buy;

Sell = 0; 

AddColumn(BarIndex(), "BarIndex");

AddColumn(posOpen, "posOpen");

AddColumn(Ref(posOpen, -1), "Ref(posOpen -1)");

AddColumn(Sell, "sell");

AddColumn(Buy, "buy");






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