Hidden Retain statement that is working without writing it

[Ronein]

Hello

Here are some examples to create serial number.

Some of them are working and some not .

I want to refresh my memory why Example1 is working without Retain statement?

Does it mean that there is hidden Retain that is working here even if we didn't write Retain statement?

Will it also work automatically when using sum(seq,1) or just when using seq+1 ?

Data have;
Input profit;
cards;
10
40 
50
;
run;

Data ex1:
set have;
seq+1;
Run;

Data ex2:
set have;
sum(seq,1);
Run;


Data ex3:
set have;
Retain seq 0;
seq+1;
Run;


Data ex4:
set have;
Retain seq 0;
seq=seq+1;
Run;

[PaigeMiller]

seq+1; has an implied RETAIN. https://documentation.sas.com/?docsetId=lestmtsref&docsetTarget=n1dfiqj146yi2cn1maeju9wo7ijs.htm&doc...

Will it work for  your other examples? Run the code and see!