Product function for Arrays

Hello,

This code may be useful for Pine script coders only.

Arrays were welcomed in Pine script, as they are a foundation for coding properly many useful things, like studies and strategies here in TradingView :)

TradingView recently released new functions for arrays, like array.median and more, but the "PRODUCT" function was still missing, so I created it. I've no doubt that array.product() will soon be proposed by the platform, but for the time being, one can use mine.

It does the same thing as the PRODUCT() function in Excel : it multiplies all the source values included in the specified lookback, and returns the product. This function can accept Series or Arrays as source input.