Hey udihamudi,
Workshop4 code can be found here
https://zorro-project.com/manual/en/tutorial_trade.htmIt should be distributed with Zorro if you downloaded the latest version.
I believe this MACD example that you're looking at is some outdated one.
There are no buyLong/sellLong functions in my Zorro 2.50
instead you're should be using something like:
vars macd = series(MACD(Prices, 12, 26, 9));
if (crossOver(macd,0)) enterLong();
else if (crossUnder(macd,0)) exitLong();
With prices like in workshop 4.