DataSeries variables

Hi, I'm trying to port some code from pine script but can't find a data series variable.  I have this:

`Hlv = 0
Hlv := close > sslsmaHigh ? 1 : close < sslsmaLow ? -1 : Hlv[1]`

how can I refer the value of Hlv variable for the bar before current Hlv[1] ?
 
thanks
