day06a.cob

       identification division.
       program-id. day06.
       
       data division.
       working-storage section.
       01 input-line pic x(100).

       01 action pic x(10).
       01 coords pic x(100).
       01 start-coords pic x(100).
       01 end-coords pic x(100).

       01 start-x pic 9(10).
       01 end-x pic 9(10).
       01 start-y pic 9(10).
       01 end-y pic 9(10).

       01 x pic 9(10).
       01 y pic 9(10).

       01 temp pic 9.
       01 matrix-table.
           05 occurs 1000 times.
               10 occurs 1000 times.
                   15 matrix pic 9 value 0.

       procedure division.
           accept input-line.
           perform input-loop-para until input-line = SPACE.

      *    Count the lit lights  
           move 0 to x.
           inspect matrix-table tallying x for all '1'.
           display x.

           stop run.

       input-loop-para.
           display input-line.
           
           if input-line(1:7) = "turn on" then
               move "turn on" to action
               move input-line(9:) to coords
           end-if.
           if input-line(1:8) = "turn off" then
               move "turn off" to action
               move input-line(10:) to coords
           end-if.
           if input-line(1:7) = "toggle" then
               move "toggle" to action
               move input-line(8:) to coords
           end-if.
           
           unstring coords delimited by " through "
               into start-coords, end-coords.

           unstring start-coords delimited by "," into start-x, start-y
           unstring end-coords delimited by "," into end-x, end-y

           move start-y to y.
           perform outer-loop-para until y > end-y.

           accept input-line.

       outer-loop-para.
           move start-x to x.
           perform inner-loop-para until x > end-x.
           add 1 to y.

       inner-loop-para.
           if action = "turn on" then
               move 1 to matrix(y + 1, x + 1).

           if action = "turn off" then
               move 0 to matrix(y + 1, x + 1).

           if action = "toggle" then
               move 1 to temp
               subtract matrix(y + 1, x + 1) from temp
               move temp to matrix(y + 1, x + 1)
           end-if.

           add 1 to x.