tasks a-s

Task/Queue-Usage/REXX/queue-usage.rexx

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+/*REXX program demonstrates three queue operations:  push, pop, queued. */
+say '══════════════════════════════════Pushing five values to the stack.'
+        do j=1 for 4                   /*loop to PUSH four values.      */
+        call push j*10                 /*PUSH  (aka enqueue to stack).  */
+        say 'pushed value:' j*10       /*echo the pushed value.         */
+        if j\==3 then iterate          /*also, insert a "null" entry.   */
+        call push                      /*PUSH  (aka enqueue to stack).  */
+        say 'pushed a "null" value.'   /*echo what was pushed.          */
+        end   /*j*/
+say '══════════════════════════════════Popping all values from the stack.'
+        do m=1 while \empty()          /*EMPTY (returns TRUE if empty). */
+        call pop                       /*POP   (aka dequeue from stack).*/
+        say m': popped value=' result  /*echo the popped value.         */
+        end   /*m*/
+say '══════════════════════════════════The stack is now empty.'
+exit                                   /*stick a fork in it, we're done.*/
+/*──────────────────────────────────subroutines/functions/operators.    */
+push:   queue arg(1);  return          /*REXX  QUEUE   is FIFO.         */
+pop:    procedure;  pull x;  return x  /*REXX PULL  removes a stack item*/
+empty:  return queued()==0             /*returns the status of the stack*/