FIFO

[Salih Dincer]

On Monday, 13 May 2024 at 15:07:39 UTC, Andy Valencia wrote:
>
> Representing the FIFO as a linked list clearly has its cost, 
> but I found the increased system time interesting.  OS memory 
> allocations maybe?

I know you want FIFO, I usually keep this on hand for fixed size 
LIFO; It can easily convert to FIFO and doesn't use LinkedList:

```d
class LIFO(T)
{
   T * element;
   size_t length, size;
   this(size_t s) {
     element = cast(T*)new T[s];
     length = s;
   }
   auto rewind() => size = length;

   bool empty() => !size;
   auto front() => element[size - 1];
   auto popFront() => --size;

   auto pop() => empty ? T(0) : element[--size];
   alias push = insertFront;
   auto insertFront(T value)
   in(size < length, "Stack is overflow!")
     => element[size++] = value;

   auto ref opDollar() => length;
   auto ref opIndex(size_t i) => element[i];
   auto ref opSlice(size_t first, size_t last)
     => element[first..last];

} unittest {

   enum test = 7;
   auto stack = new LIFO!size_t(test);

   assert(!stack.size);
   foreach (prime; 1..test + 1)
   {
     stack.insertFront(prime);
   }
   assert(stack.size == test); // == 7

   stack.writeln(": ", stack.length); // [7, 6, 5, 4, 3, 2, 1]: 7
   stack[$/2].writeln("-", stack[0]); // 4-1


   stack.rewind();
   stack.size.write(": ["); // 10:
   while (auto next = stack.pop)
   {
     if (next == 1) next.writeln("]");
     else next.write(", ");
   }
   stack.size.writeln; // 0
   stack.rewind();
   assert(stack.size == test);
}

SDB at 79