How to compare 2 adjacent values when using %do %until in SAS

[Poisonous_Snake]

No, although there is a series of intervals, but these are intervals of A, so if these intervals are overlap, it means you use A continuously, (you can image that you are delivered candy A 4 times, but because the period of each candy A delivrance is overlap, so you eat candy A everyday sans cease), in that case, I know to know if the interval from the begin of A (the first time delivering candy A) to the end of A (the time you eat your last candy A) is cover interval of B (supposed that is a new kind of candy B).
In case of these intervals of A are disrupted, which means you have some seperated intervals of A, so when the interval of B fall in these intervals of A, it is not covered.
There is another case that only one interval or two intervals of A can cover interval of B.
And I only want to know if interval of B is completely covered by interval(s) of A.

[Tom]

I can see two methods to fix this. 

One is to first collapse your A intervals so that they do represent separate intervals. Then loop over them and check if B falls in any of them.

The other is to brute force it.  Make a large temporary array with one element for each possible day.  Process the A records to fill in the days each covers. Then loop of the days of the B interval and see if all of the days are covered.

[Poisonous_Snake]

I think about collapse the intervals of A into only one interval of A (if they are overlap), so now I'm trying to do it, although there are some problems (because there are more conditions for A and B), but that's the only way I can do right now. 

For your second solution, I don't really understand it.

Thank you for helping me hihi