ok... then what should I do to compile

// don't trade when the equity curve goes down
// and is below its own lowpass filtered value
function checkEquity()
{
// generate equity curve including phantom trades
vars EquityCurve = series(EquityLong+EquityShort);
vars EquityLP = series(LowPass(EquityCurve,10));
if(EquityLP[0] < LowPass(EquityLP,100) && falling(EquityLP))
setf(TradeMode,TR_PHANTOM); // drawdown -> phantom trades
else
resf(TradeMode,TR_PHANTOM); // profitable -> normal trades
}

? It's from the manual, I'm using Zorro 1.66. Am I missing a header file?