Set and Array Indexing and Size Within SAS OR Constraint Statement With Conditional Logic

[yus03590]

Hi, I haven't used SAS in some time and so I'm somewhat rusty, and my organization will start using SAS OR soon. To prepare I've devised a practice problem for myself.  

I'm optimizing a simple employee schedule and have the following constraint where each shift length must be at least 3 hours.

Assigned shifts are represented using a two dimensional array as shown below.

employee    8-9     9-10    10-11   etc
jack        0       1       1       
mark        0       0       0       
jane        1       1       1       
etc

1 means that employee is assigned to that time and 0 means they are not.  The array is declared with sets (I will read in the contents of the sets, so the size is variable).  Below is the declaration.

set <string> employees;
set <string> shifts;
num assignedShifts{employees, shifts}

Below is the code for the constraint.

dcl num index;
dcl num sum;
constraint shiftLength{e in employees, s in shifts}: 
*need to introduce logic to separate morning/afeternoon shift requirements;
    if assignedShifts{e, s} = 1 then do;
        *does this assignment statement work?;
        index = s;
        sum = 0;
        *need to somehow get set size to check bounderies;
        do while(assignedShifts{e, index});
            sum = sum + assignedShifts{e, index};
            index = index + 1;
        end;
        s = index;
    end;
    sum >= 3;

The logic I have devised for checking if each shift is three hours or not is to sum each consecutive assignment value until I run into a 0. 

Question 1: I declare a numerical index, assign the value of s to it, increment the index variable, then re-assigned the it's value to s.  Is this valid?  If not then how would I accomplish this?

Question 2: The code I have will throw an "index out of bounds" error because I don't check that index is within the number of shifts.  The number of shifts is variable since I read in the set.  How do I check the size of the set at run time?

Question 3: Say I have another shift length constraint that only checks shifts in the afternoon.  How would I set s to "start" at an nth value in set shifts (or to stop at an nth)?

Thanks for your help!

[RobPratt]

Your constraint declaration should use algebraic expressions instead of programming statements.  You might find this documentation example helpful as a starting point for your scheduling problem.

This book of examples is also useful.