September Morn Update

Task/Stack/ABAP/stack.abap

@@ -0,0 +1,205 @@
+report z_stack.
+
+interface stack.
+  methods:
+    push
+      importing
+        new_element      type any
+      returning
+        value(new_stack) type ref to stack,
+
+    pop
+      exporting
+        top_element      type any
+      returning
+        value(new_stack) type ref to stack,
+
+    empty
+      returning
+        value(is_empty) type abap_bool,
+
+    peek
+      exporting
+        top_element type any,
+
+    get_size
+      returning
+        value(size) type int4,
+
+    stringify
+      returning
+        value(stringified_stack) type string.
+endinterface.
+
+
+class character_stack definition.
+  public section.
+    interfaces:
+      stack.
+
+
+    methods:
+      constructor
+        importing
+          characters type string optional.
+
+
+  private section.
+    data:
+      characters type string.
+endclass.
+
+
+class character_stack implementation.
+  method stack~push.
+    characters = |{ new_element }{ characters }|.
+
+    new_stack = me.
+  endmethod.
+
+
+  method stack~pop.
+    if not me->stack~empty( ).
+      top_element = me->characters(1).
+
+      me->characters = me->characters+1.
+    endif.
+
+    new_stack = me.
+  endmethod.
+
+
+  method stack~empty.
+    is_empty = xsdbool( strlen( me->characters ) eq 0 ).
+  endmethod.
+
+
+  method stack~peek.
+    check not me->stack~empty( ).
+
+    top_element = me->characters(1).
+  endmethod.
+
+
+  method stack~get_size.
+    size = strlen( me->characters ).
+  endmethod.
+
+
+  method stack~stringify.
+    stringified_stack = cond string(
+      when me->stack~empty( )
+      then `empty`
+      else me->characters ).
+  endmethod.
+
+
+  method constructor.
+    check characters is not initial.
+
+    me->characters = characters.
+  endmethod.
+endclass.
+
+
+class integer_stack definition.
+  public section.
+    interfaces:
+      stack.
+
+
+    methods:
+      constructor
+        importing
+          integers type int4_table optional.
+
+
+  private section.
+    data:
+      integers type int4_table.
+endclass.
+
+
+class integer_stack implementation.
+  method stack~push.
+    append new_element to me->integers.
+
+    new_stack = me.
+  endmethod.
+
+
+  method stack~pop.
+    if not me->stack~empty( ).
+      top_element = me->integers[ me->stack~get_size( ) ].
+
+      delete me->integers index me->stack~get_size( ).
+    endif.
+
+    new_stack = me.
+  endmethod.
+
+
+  method stack~empty.
+    is_empty = xsdbool( lines( me->integers ) eq 0 ).
+  endmethod.
+
+
+  method stack~peek.
+    check not me->stack~empty( ).
+
+    top_element = me->integers[ lines( me->integers ) ].
+  endmethod.
+
+
+  method stack~get_size.
+    size = lines( me->integers ).
+  endmethod.
+
+
+  method stack~stringify.
+    stringified_stack = cond string(
+      when me->stack~empty( )
+      then `empty`
+      else reduce string(
+        init stack = ``
+        for integer in me->integers
+        next stack = |{ integer }{ stack }| ) ).
+  endmethod.
+
+
+  method constructor.
+    check integers is not initial.
+
+    me->integers = integers.
+  endmethod.
+endclass.
+
+
+start-of-selection.
+  data:
+    stack1        type ref to stack,
+    stack2        type ref to stack,
+    stack3        type ref to stack,
+
+    top_character type char1,
+    top_integer   type int4.
+
+  stack1 = new character_stack( ).
+  stack2 = new integer_stack( ).
+  stack3 = new integer_stack( ).
+
+  write: |Stack1 = { stack1->stringify( ) }|, /.
+  stack1->push( 'a' )->push( 'b' )->push( 'c' )->push( 'd' ).
+  write: |push a, push b, push c, push d -> Stack1 = { stack1->stringify( ) }|, /.
+  stack1->pop( )->pop( importing top_element = top_character ).
+  write: |pop, pop and return element -> { top_character }, Stack1 = { stack1->stringify( ) }|, /, /.
+
+  write: |Stack2 = { stack2->stringify( ) }|, /.
+  stack2->push( 1 )->push( 2 )->push( 3 )->push( 4 ).
+  write: |push 1, push 2, push 3, push 4 -> Stack2 = { stack2->stringify( ) }|, /.
+  stack2->pop( )->pop( importing top_element = top_integer ).
+  write: |pop, pop and return element -> { top_integer }, Stack2 = { stack2->stringify( ) }|, /, /.
+
+  write: |Stack3 = { stack3->stringify( ) }|, /.
+  stack3->pop( ).
+  write: |pop -> Stack3 = { stack3->stringify( ) }|, /, /.

Task/Stack/Elena/stack.elena

@@ -1,9 +1,12 @@
-    var stack := system'collections'Stack new.
+public program()
+{
+    var stack := new system'collections'Stack();
 
-    stack push:2.
+    stack.push:2;
 
-    var isEmpty := stack length == 0.
+    var isEmpty := stack.Length == 0;
 
-    var item := stack peek. // Peek without Popping.
+    var item := stack.peek(); // Peek without Popping.
 
-    item := stack pop.
+    item := stack.pop()
+}

Task/Stack/Free-Pascal/stack.free

@@ -0,0 +1,23 @@
+program Stack;
+ {$IFDEF FPC}{$MODE DELPHI}{$IFDEF WINDOWS}{$APPTYPE CONSOLE}{$ENDIF}{$ENDIF}
+ {$ASSERTIONS ON}
+uses Generics.Collections;
+
+var
+  lStack: TStack<Integer>;
+begin
+  lStack := TStack<Integer>.Create;
+  try
+    lStack.Push(1);
+    lStack.Push(2);
+    lStack.Push(3);
+    Assert(lStack.Peek = 3); // 3 should be at the top of the stack
+
+    Write(lStack.Pop:2);   // 3
+    Write(lStack.Pop:2);   // 2
+    Writeln(lStack.Pop:2); // 1
+    Assert(lStack.Count = 0, 'Stack is not empty'); // should be empty
+  finally
+    lStack.Free;
+  end;
+end.

Task/Stack/OCaml/stack.ocaml

@@ -5,7 +5,7 @@ class ['a] stack =
     val mutable lst : 'a list = []
 
     method push x =
-     lst <- x::lst
+      lst <- x::lst
 
     method pop =
       match lst with

Task/Stack/Racket/stack-1.rkt

@@ -1,5 +1,5 @@
 #lang racket
-(define (stack) '())
+(define stack '())
 (define (push x stack) (cons x stack))
 (define (pop stack) (values (car stack) (cdr stack)))
 (define (empty? stack) (null? stack))

Task/Stack/Ruby/stack-4.rb

@@ -0,0 +1,11 @@
+require 'forwardable'
+
+class Stack
+  extend Forwardable
+
+  def initialize
+    @stack = []
+  end
+
+  def_delegators :@stack, :push, :pop, :empty?
+end

Task/Stack/VBScript/stack-2.vb

@@ -0,0 +1,39 @@
+' Stack Definition - VBScript
+
+Option Explicit
+
+Dim stack, i, x
+Set stack = CreateObject("System.Collections.ArrayList")
+If Not empty_(stack) Then Wscript.Echo stack.Count
+push stack, "Banana"
+push stack, "Apple"
+push stack, "Pear"
+push stack, "Strawberry"
+Wscript.Echo "Count=" & stack.Count 		    ' --> Count=4
+Wscript.Echo pop(stack) & " - Count=" & stack.Count ' --> Strawberry - Count=3
+Wscript.Echo "Tail=" & stack.Item(0) 		    ' --> Tail=Banana
+Wscript.Echo "Head=" & stack.Item(stack.Count-1)    ' --> Head=Pear
+Wscript.Echo stack.IndexOf("Apple", 0)   	    ' --> 1
+For i=1 To stack.Count
+	Wscript.Echo join(stack.ToArray(), ", ")
+	x = pop(stack)
+Next 'i
+
+Sub push(s, what)
+    s.Add what
+End Sub 'push
+
+Function pop(s)
+	Dim what
+    If s.Count > 0 Then
+        what = s(s.Count-1)
+        s.RemoveAt s.Count-1
+    Else
+        what = ""
+    End If
+    pop = what
+End Function 'pop
+
+Function empty_(s)
+    empty_ = s.Count = 0
+End Function 'empty_