What is a variable period?

[kgalea]

Hi.
Reading through AFL reference guide. I came up to this section. Didnt find anything that explained what it is, why we need it ect.

Variable period functions

Functions accepting variable periods....

Cheers

[fxshrat]

Variable periods are periods that are of type ARRAY.
Such periods may be different per each element of array.
Here is example where period is variable one:

new_day = Datenum() != Ref(DateNum(),-1);
period = BarsSince(new_day)+1;
x = Sum(V, period);

Non-variable (fix) period (-> just single value):

period = 10;
x = Sum(V, period);

[kgalea]

Thank you for taking the time to answer my question