I ask for help from MT4 developers (MQL), what is this line of code?

Question

C++ / C#

Can you at least say what it could be?
And what output can be the test variable?
I would like as much detail as possible what types are there and what is happening in general, if anyone knows.

test = (iRSI(Symbol(), 0, 30, PRICE_OPEN, 15) - 50.0) / 50.0;

I dug up what iRSI is, it's like a Relative Strength Index technical indicator.

Answer 1

I dug up what iRSI is, it's like a Relative Strength Index technical indicator.

The first link in the search for "iRSI" says the same thing, and describes what's going on in your line of code.
Generally without problems (on the first link in the search):

double  iRSI(
   string       symbol,           // имя символа
   int          timeframe,        // таймфрейм
   int          period,           // период
   int          applied_price,    // тип цены
   int          shift             // сдвиг
   );

Obviously double (by code above)
We got the RSI value 15 bars ago, subtracted 50 and then divided it by 50. In total, with such manipulations, a coefficient from -1 to 1 is obtained and it is already analyzed somehow, apparently in the future.
So if we go back to the question:
then you can simply answer: the result is in the range [-1; 1], and a more accurate figure depends on the currency pair and period in question.

Answer 2

There is a site with a similar name for questions on this topic.