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

Task/Stack/Elixir/stack.elixir

@@ -0,0 +1,12 @@
+defmodule Stack do
+  def new, do: []
+
+  def empty?([]), do: true
+  def empty?(_), do: false
+
+  def pop([h|t]), do: {h,t}
+
+  def push(h,t), do: [h|t]
+
+  def top([h|_]), do: h
+end

Task/Stack/Ruby/stack-2.rb

@@ -41,25 +41,15 @@ class Stack
   # If passing a number _n_, removes the top _n_ elements, and returns
   # an Array of them. If this Stack contains fewer than _n_ elements,
   # returns them all. If this Stack is empty, returns an empty Array.
-  nil
+  def_delegator :@ary, :pop
 
-  if ([].pop(0) rescue false)
-    # Ruby >= 1.8.7
-    def_delegator :@ary, :pop
-  else
-    # Ruby < 1.8.7
-    def pop(*args)  # :nodoc:
-      case len = args.length
-      when 0
-        @ary.pop
-      when 1
-        n = [@ary.length, args.first].min
-        @ary.slice!(-n, n)
-      else
-        raise ArgumentError, "wrong number of arguments (#{len} for 0..1)"
-      end
-    end
-  end
+  ##
+  # :method: top
+  # :call-seq:
+  #   top -> obj or nil
+  #   top(n) -> ary
+  # Returns the topmost element without modifying the stack.
+  def_delegator :@ary, :last, :top
 
   ##
   # :method: empty?

Task/Stack/Ruby/stack-3.rb

@@ -1,12 +1,19 @@
-s = Stack.new
-s.empty?                           # => true
-s.pop                              # => nil
-s.pop(1)                           # => []
-s.push(1)                          # => Stack[1]
-s.push(2, 3)                       # => Stack[1, 2, 3]
-s.pop                              # => 3
-s.pop(1)                           # => [2]
-s.empty?                           # => false
+p s = Stack.new                 # => Stack[]
+p s.empty?                      # => true
+p s.size                        # => 0
+p s.top                         # => nil
+p s.pop                         # => nil
+p s.pop(1)                      # => []
+p s.push(1)                     # => Stack[1]
+p s.push(2, 3)                  # => Stack[1, 2, 3]
+p s.top                         # => 3
+p s.top(2)                      # => [2, 3]
+p s                             # => Stack[1, 2, 3]
+p s.size                        # => 3
+p s.pop                         # => 3
+p s.pop(1)                      # => [2]
+p s.empty?                      # => false
 
-s = Stack[:a, :b, :c]
-s.pop                              # => :c
+p s = Stack[:a, :b, :c]         # => Stack[:a, :b, :c]
+p s << :d                       # => Stack[:a, :b, :c, :d]
+p s.pop                         # => :d