Re: Need OCCURS when defining data structures

Adam Glauser wrote:

Thanks for bringing that up ... this could be a really nice way to implement queues and stacks of fixed-length elements.

Shifting the entire array each time could be punishing for performance depending on the size of each element.

For a stack, it's easy to add new elements at the end, and just decrement the number of elements to pop them off.

For a queue, you can keep a circular array, where the logical first element is not necessarily arr(1). arr(1) may logically follow arr(max).

Example: arr has 20 actual elements
Actual values are cde...............ab
arrFirst = 19
arrNum = 5
arrLast = 3
Logical values are abcde

Remove an element from the beginning of the queue:
arrFirst += 1
if arrFirst > %elem(arr)
arrFirst = 1

Add an element to the end of the queue
arrNum += 1
if arrNum > %elem(arr)
error
arrLast += 1
if arrLast > %elem(arr)
arrLast = 1
arr(arrLast) = newvalue

Process the queue in order
i = arrFirst
for x = 1 to arrNum
process(arr(i))
i += 1
if i > %elem(arr)
i = 1
endfor