Another update from ingydotnet^djgoku

Task/Stack/ALGOL-68/stack-5.alg

@@ -0,0 +1,45 @@
+MODE DIETITEM = STRUCT (
+  STRING food, annual quantity, units, REAL cost
+);
+
+MODE OBJVALUE = DIETITEM;
+
+# PUSH element to stack #
+OP +:= = (REF FLEX[]OBJVALUE stack, OBJVALUE item) VOID:
+   BEGIN
+      FLEX[UPB stack + 1]OBJVALUE newstack;
+      newstack[2:UPB newstack] := stack;
+      newstack[1] := item;
+      stack := newstack
+   END;
+
+OP POP = (REF FLEX[]OBJVALUE stack) OBJVALUE:
+   IF UPB stack > 0 THEN
+      OBJVALUE result = stack[1];
+      stack := stack[2:UPB stack];
+      result
+   ELSE
+      # raise index error; # SKIP
+   FI;
+
+# Stigler's 1939 Diet ... #
+FORMAT diet item fmt = $g": "g" "g" = $"zd.dd$;
+[]DIETITEM stigler diet = (
+  ("Cabbage",           "111","lb.",  4.11),
+  ("Dried Navy Beans",  "285","lb.", 16.80),
+  ("Evaporated Milk",    "57","cans", 3.84),
+  ("Spinach",            "23","lb.",  1.85),
+  ("Wheat Flour",       "370","lb.", 13.33),
+  ("Total Annual Cost",    "","",    39.93)
+);
+
+FLEX[0]DIETITEM example stack;
+
+FOR i TO UPB stigler diet DO
+   example stack +:= stigler diet[i]
+OD;
+
+printf($"Items popped in reverse:"l$);
+WHILE UPB example stack > 0 DO
+  printf((diet item fmt, POP example stack, $l$))
+OD