26 files changed, 954 insertions, 0 deletions

diff --git a/arrays/arrays.gpr b/arrays/arrays.gpr
new file mode 100644
index 0000000..3d7ea37
--- /dev/null
+++ b/arrays/arrays.gpr
@@ -0,0 +1,5 @@
+project Arrays is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("arrays.adb");
+end Arrays;
diff --git a/arrays/src/arrays.adb b/arrays/src/arrays.adb
new file mode 100644
index 0000000..e851fc6
--- /dev/null
+++ b/arrays/src/arrays.adb
@@ -0,0 +1,127 @@
+with Ada.Text_IO;           use Ada.Text_IO;
+with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
+
+procedure Arrays is
+  -----------------------------------------------------------------------------
+  -- Arrays 101.
+  --
+  -- The index is strongly-typed and can be any discrete type.
+  --
+  -- Iterations over the index type are preferred over iterations over specific
+  -- index values.
+  -----------------------------------------------------------------------------
+  procedure Test_Array is
+    type My_Int is range 0 .. 1_000;
+    type Index is range 1 .. 5;
+
+    type My_Int_Array is array (Index) of My_Int;
+
+    function To_String (A : My_Int_Array) return String is
+      S : Unbounded_String;
+    begin
+      for I in Index loop
+        S := S & My_Int'Image (A (I)) & " ";
+      end loop;
+      return To_String (S);
+    end To_String;
+
+    Arr : My_Int_Array := (2, 3, 5, 7, 11);
+    -- This array is not actually empty; its size is determined by the range of
+    -- its index type, which in this example is 1 .. 5.
+    Empty_Arr : My_Int_Array;
+  begin
+    Put_Line ("Arr = " & To_String (Arr));
+    Put_Line ("Arr is " & Integer'Image (Arr'Size) & " bytes");
+
+    Put_Line ("Empty_Arr = " & To_String (Empty_Arr));
+    Put_Line ("Empty_Arr is " & Integer'Image (Empty_Arr'Size) & " bytes");
+  end Test_Array;
+
+  -----------------------------------------------------------------------------
+  -- Enums as array indices.
+  -----------------------------------------------------------------------------
+  procedure Test_Enum_Array is
+    type Month is (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec);
+    type Day is range 1 .. 31;
+
+    Month_Days : array (Month) of Day :=
+     (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
+  begin
+    for M in Month loop
+      Put_Line
+       (Month'Image (M) & " has " & Day'Image (Month_Days (M)) & " days");
+    end loop;
+  end Test_Enum_Array;
+
+  -----------------------------------------------------------------------------
+  -- Arrays in ADA are bounds-checked.
+  -----------------------------------------------------------------------------
+  procedure Test_Bounds is
+    Arr : array (Integer range 1 .. 5) of Integer := (3, 4, 7, 8, 9);
+  begin
+    Arr (1) := 17;
+    Arr (5) := 18;
+    --Arr (6) := 19; -- Error.
+  end Test_Bounds;
+
+  -----------------------------------------------------------------------------
+  -- Use the Range attribute to iterate over an array with an anonymous range.
+  -----------------------------------------------------------------------------
+  procedure Test_Anonymous_Range is
+    Arr : array (3 .. 7) of Integer := (5, 8, 3, 5, 3);
+  begin
+    for I in Arr'Range loop
+      Put_Line
+       ("Index " & Integer'Image (I) & " has value " &
+        Integer'Image (Arr (I)));
+    end loop;
+  end Test_Anonymous_Range;
+
+  -----------------------------------------------------------------------------
+  -- Unconstrained arrays.
+  --
+  -- The size/bounds are provided when creating an instance of the array type.
+  -----------------------------------------------------------------------------
+  procedure Test_Unbounded_Array is
+    type Day is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
+    type Days_Arr is array (Integer range <>) of Day;
+
+    Days_Off : Days_Arr := (Sat, Sun);
+  begin
+    Put ("Holidays: ");
+    for D in Days_Off'Range loop
+      Put (Day'Image (Days_Off (D)) & " ");
+    end loop;
+    New_Line;
+  end Test_Unbounded_Array;
+
+  -----------------------------------------------------------------------------
+  -- Bounds are automatically inferred from the initialization value.
+  -----------------------------------------------------------------------------
+  procedure Test_Auto_Bounds is
+    Arr : array (Natural range <>) of Integer := (2, 3, 4);
+  begin
+    for I in Arr'First .. Arr'Last loop
+      Put_Line ("Arr(" & Integer'Image (I) & ") = " & Integer'Image (Arr (I)));
+    end loop;
+  end Test_Auto_Bounds;
+
+  -----------------------------------------------------------------------------
+  -- Array slices.
+  -----------------------------------------------------------------------------
+  procedure Test_Slices is
+    Str : String := "Hello world";
+  begin
+    Str (7 .. 11) := "there";
+    Put_Line (Str);
+  end Test_Slices;
+
+begin
+  Test_Array;
+  Test_Enum_Array;
+  Test_Bounds;
+  Test_Anonymous_Range;
+  Test_Unbounded_Array;
+  Test_Auto_Bounds;
+  Test_Slices;
+end Arrays;
diff --git a/basics/basics.gpr b/basics/basics.gpr
new file mode 100644
index 0000000..a217eed
--- /dev/null
+++ b/basics/basics.gpr
@@ -0,0 +1,5 @@
+project Basics is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("main.adb");
+end Basics;
diff --git a/basics/src/main.adb b/basics/src/main.adb
new file mode 100644
index 0000000..63339ae
--- /dev/null
+++ b/basics/src/main.adb
@@ -0,0 +1,108 @@
+with Ada.Text_IO; use Ada.Text_IO;
+with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
+
+procedure Main is
+   procedure Read_Number is
+      N : Integer;
+   begin
+      Put_Line ("Please enter a number");
+      Get (N);
+      if N > 0 then
+         Put_Line ("The number is positive");
+      elsif N = 0 then
+         Put_Line ("The number is zero");
+      else
+         Put_Line ("The number is negative");
+      end if;
+   end Read_Number;
+
+   procedure Test_Loop is
+      N : Integer := 0;
+   begin
+      loop
+         exit when N = 5;
+         N := N + 1;
+         Put_Line ("Test loop");
+      end loop;
+   end Test_Loop;
+
+   procedure Test_Even_Odd is
+   begin
+      for I in 0 .. 10 loop
+         Put_Line (I'Image & " is " & (if I mod 2 = 1 then "Odd" else "Even"));
+      end loop;
+   end Test_Even_Odd;
+
+   procedure My_Swap (A : in out Integer; B : in out Integer) is
+      C : Integer;
+   begin
+      C := A;
+      A := B;
+      B := C;
+   end My_Swap;
+
+   procedure Test_My_Swap is
+      A : Integer := 1;
+      B : Integer := 3;
+   begin
+      Put_Line ("Before swap: " & A'Image & B'Image);
+      My_Swap (A, B);
+      Put_Line ("After swap: " & A'Image & B'Image);
+   end Test_My_Swap;
+
+   function Fib (N : Integer) return Integer is
+      F0 : Integer := 0;
+      F1 : Integer := 1;
+      F  : Integer := 0;
+   begin
+      for I in 2 .. N loop
+         F := F0 + F1;
+         F0 := F1;
+         F1 := F;
+      end loop;
+      return F;
+   end Fib;
+
+   function Factorial (N : Integer) return Integer is
+      F : Integer := 1;
+   begin
+      for I in 2 .. N loop
+         F := F * I;
+      end loop;
+      return F;
+   end Factorial;
+
+   procedure Test_Functions is
+      N : Integer;
+   begin
+      Put_Line ("Enter a number:");
+      Get (N);
+      Put_Line ("Fib(" & N'Image & ") = " & Fib (N)'Image);
+      Put_Line ("Factorial(" & N'Image & ") = " & Factorial (N)'Image);
+   end Test_Functions;
+
+   procedure Test_Integers is
+      type Day is range 1 .. 7;
+      My_Day : Day := 3;
+      Other_Day : Day;
+   begin
+      for D in Day loop
+         Put_Line ("Day" & D'Image);
+      end loop;
+      Put_Line (My_Day'Image);
+      Other_Day := My_Day + Day (4);
+      Put_Line (Other_Day'Image);
+   end Test_Integers;
+
+begin
+   -- This is a comment.
+   Put_Line ("Hello world!");
+
+   Test_Loop;
+   Test_Even_Odd;
+   Test_My_Swap;
+   Test_Integers;
+
+   --Read_Number;
+   Test_Functions;
+end Main;
diff --git a/guess/guess.gpr b/guess/guess.gpr
new file mode 100644
index 0000000..ee53cfa
--- /dev/null
+++ b/guess/guess.gpr
@@ -0,0 +1,5 @@
+project Guess is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("guess.adb");
+end Guess;
diff --git a/guess/src/guess.adb b/guess/src/guess.adb
new file mode 100644
index 0000000..dc394fa
--- /dev/null
+++ b/guess/src/guess.adb
@@ -0,0 +1,20 @@
+with Ada.Text_IO;         use Ada.Text_IO;
+with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
+
+procedure Guess is
+  Answer : Integer := 47;
+  Guess  : Integer;
+begin
+  loop
+    Put ("Enter a number: ");
+    Get (Guess);
+    if Guess < Answer then
+      Put_Line ("Too low!");
+    elsif Guess > Answer then
+      Put_Line ("Too high!");
+    elsif Guess = Answer then
+      Put_Line ("Correct!");
+    end if;
+    exit when Guess = Answer;
+  end loop;
+end Guess;
diff --git a/hello/hello.gpr b/hello/hello.gpr
new file mode 100644
index 0000000..3f34ae9
--- /dev/null
+++ b/hello/hello.gpr
@@ -0,0 +1,5 @@
+project Hello is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("main.adb");
+end Hello;
diff --git a/hello/src/main.adb b/hello/src/main.adb
new file mode 100644
index 0000000..c9cb966
--- /dev/null
+++ b/hello/src/main.adb
@@ -0,0 +1,108 @@
+with Ada.Text_IO;         use Ada.Text_IO;
+with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
+
+procedure main is
+
+  function Factorial (N : Integer) return Integer is
+    F : Integer := 1;
+  begin
+    for i in 2 .. N loop
+      F := F * i;
+    end loop;
+    return F;
+  end Factorial;
+
+  function Fib (N : Integer) return Integer is
+    F : array (0 .. N) of Integer;
+  begin
+    F (0) := 0;
+    F (1) := 1;
+    for I in F'First + 2 .. F'Last loop
+      F (I) := F (I - 2) + F (I - 1);
+    end loop;
+    return F (N);
+  end Fib;
+
+  function Fib_Rec (N : Integer) return Integer is
+  begin
+    if N = 0 then
+      return 0;
+    elsif N = 1 then
+      return 1;
+    else
+      return Fib_Rec (N - 1) + Fib_Rec (N - 2);
+    end if;
+  end Fib_Rec;
+
+  procedure Greet_5 is
+    counter : Integer := 1;
+  begin
+    Put_Line ("Greet_5");
+    loop
+      Put_Line ("Counter: " & Integer'Image (counter));
+      exit when counter = 5;
+      counter := counter + 1;
+    end loop;
+  end Greet_5;
+
+  procedure Greet_With_While is
+    counter : Integer := 1;
+  begin
+    Put_Line ("Greet_With_While");
+    while counter <= 5 loop
+      Put_Line ("Counter: " & Integer'Image (counter));
+      counter := counter + 1;
+    end loop;
+  end Greet_With_While;
+
+  procedure Swap (A, B : in out Integer) is
+    Tmp : Integer;
+  begin
+    Tmp := A;
+    A   := B;
+    B   := Tmp;
+  end Swap;
+
+  procedure Guessing_Game is
+    Answer : Integer := 47;
+    Guess  : Integer;
+  begin
+    loop
+      Put ("Enter a number: ");
+      Get (Guess);
+      if Guess < Answer then
+        Put_Line ("Too low!");
+      elsif Guess > Answer then
+        Put_Line ("Too high!");
+      else
+        Put_Line ("Correct!");
+        exit;
+      end if;
+    end loop;
+  end Guessing_Game;
+
+  N : Integer;
+  X : Integer := 2;
+  Y : Integer := 3;
+
+begin
+  Put ("Enter an integer value: ");
+  Get (N);
+  if N >= 0 then
+    Put_Line ("Fib(" & Integer'Image (N) & ") = " & Integer'Image (Fib (N)));
+    Put_Line
+     ("Factorial(" & Integer'Image (N) & ") = " &
+      Integer'Image (Factorial (N)));
+  else
+    Put_Line ("Please enter a non-negative integer");
+  end if;
+
+  Greet_5;
+  Greet_With_While;
+
+  Put_Line ("Swapping " & Integer'Image (X) & " and " & Integer'Image (Y));
+  Swap (X, Y);
+  Put_Line ("X = " & Integer'Image (X) & ", Y = " & Integer'Image (Y));
+
+  Guessing_Game;
+end main;
diff --git a/list/list.gpr b/list/list.gpr
new file mode 100644
index 0000000..5095383
--- /dev/null
+++ b/list/list.gpr
@@ -0,0 +1,5 @@
+project List is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("list.adb");
+end List;
diff --git a/list/src/list.adb b/list/src/list.adb
new file mode 100644
index 0000000..c8910d6
--- /dev/null
+++ b/list/src/list.adb
@@ -0,0 +1,46 @@
+with Ada.Text_IO; use Ada.Text_IO;
+
+procedure List is
+
+  type MyList;
+
+  type MyList_Access is access MyList;
+
+  type MyList is record
+    Value : Integer       := 0;
+    Next  : MyList_Access := null;
+  end record;
+
+  function Length (XS : access constant MyList) return Integer is
+    L    : Integer                := 0;
+    Node : access constant MyList := XS;
+  begin
+    while Node /= null loop
+      L    := L + 1;
+      Node := Node.Next;
+    end loop;
+    return L;
+  end Length;
+
+  procedure Print_List (XS : access constant MyList) is
+  begin
+    if XS /= null then
+      Put (Integer'Image (XS.Value) & " ");
+      Print_List (XS.Next);
+    end if;
+  end Print_List;
+
+  function Build_List return MyList_Access is
+    XS : MyList_Access := new MyList'(1, new MyList'(2, new MyList'(3, null)));
+  begin
+    return XS;
+  end Build_List;
+
+  XS : MyList_Access := Build_List;
+
+begin
+  Put ("List: ");
+  Print_List (XS);
+  New_Line;
+  Put_Line ("The list has length " & Integer'Image (Length (XS)));
+end List;
diff --git a/more-types/src/types.adb b/more-types/src/types.adb
new file mode 100644
index 0000000..4e7590f
--- /dev/null
+++ b/more-types/src/types.adb
@@ -0,0 +1,116 @@
+with Ada.Text_IO; use Ada.Text_IO;
+
+procedure Types is
+
+   -----------------------------------------------------------------------------
+   -- Record initialization.
+   -----------------------------------------------------------------------------
+   procedure Test_Point is
+      type Point is record
+         X : Integer := 0;
+         Y : Integer := 0;
+      end record;
+
+      Origin_1 : Point;                       -- Default initialization.
+      Origin_2 : Point := (0, 0);             -- Explicit, unnamed.
+      Origin_3 : Point := (X => 0, Y => 0);   -- Explicit, named.
+      Origin_4 : Point := (X => <>, Y => <>); -- Explicit, using defaults.
+      Origin_5 : Point := (X | Y => 0);       -- Initialize both values.
+      Origin_6 : Point := Point'(0,0);        -- Qualified expression.
+   begin
+      Put_Line ("Origin: " & Integer'Image (Origin_5.X) & ", "
+                & Integer'Image (Origin_5.Y));
+   end Test_Point;
+
+   -----------------------------------------------------------------------------
+   -- Pointers.
+   -----------------------------------------------------------------------------
+   procedure Test_Pointer is
+      type Month_Type is (Jan, Feb, Mar, Apr, May, Jun,
+                          Jul, Aug, Sep, Oct, Nov, Dec);
+
+      type Date is record
+         Day : Integer range 1 .. 31;
+         Month : Month_Type;
+         Year : Integer;
+      end record;
+
+      -- Access types are nominally typed, not structurally typed.
+      -- If we "own" a type X, we typically also declare an access type named
+      -- X_Acc, so that there is a canonical name for the access type to X.
+      type Date_Acc is access Date; -- Pointer to Date type.
+      type Different_Date_Acc is access Date; -- Different type.
+
+      Null_Date : Date_Acc := null;
+
+      -- Allocate values of the access type using the 'new' keyword.
+      D : Date_Acc := new Date;
+
+      -- Constraints can be given when instantiating the type.
+      Buffer : access String := new String(1 .. 5);
+
+      -- We can also initialize along with the allocation.
+      Hello_Str : access String := new String'("Hello");
+
+      procedure Test_Null (D : Date_Acc; Name : String) is
+      begin
+         -- Dereferencing of D happens implicitly. Here we can treat D as an
+         -- actual Date.
+         if D = null then
+            Put_Line (Name & " is null");
+         else
+            Put_Line (Name & " is not null");
+         end if;
+      end Test_Null;
+
+   begin
+      Test_Null (Null_Date, "Null_Date");
+      Test_Null (D, "D");
+   end Test_Pointer;
+
+   -----------------------------------------------------------------------------
+   -- Mutually recursive types.
+   --
+   -- Similar to C++, we can forward-declare a type to break the loop.
+   -----------------------------------------------------------------------------
+
+   procedure Test_MyList is
+      type MyList;
+      type MyList_Acc is access MyList;
+
+      type MyList is record
+         Value : Integer := 0;
+         Next  : MyList_Acc := null;
+      end record;
+
+      function Cons (X : Integer; L : MyList_Acc) return MyList_Acc is
+         Head : MyList_Acc := new MyList;
+      begin
+         Head.Value := X;
+         Head.Next := L;
+         return Head;
+      end Cons;
+
+      procedure Print_List (L : access constant MyList) is
+         Node : access constant MyList := L;
+      begin
+         Put ("[");
+         while Node /= null loop
+            Put (Integer'Image (Node.Value) & " ");
+            Node := Node.next;
+         end loop;
+         Put_Line ("]");
+      end Print_List;
+
+      InitialList : MyList_Acc := new MyList'(4, null);
+      ModifiedList : MyList_Acc;
+   begin
+      ModifiedList := Cons (1, Cons (2, Cons (3, InitialList)));
+      Print_List (ModifiedList);
+   end Test_MyList;
+
+begin
+   Test_Point;
+   Test_Pointer;
+   Test_MyList;
+end Types;
diff --git a/more-types/types.gpr b/more-types/types.gpr
new file mode 100644
index 0000000..740bcfd
--- /dev/null
+++ b/more-types/types.gpr
@@ -0,0 +1,5 @@
+project Types is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("types.adb");
+end Types;
diff --git a/records/records.gpr b/records/records.gpr
new file mode 100644
index 0000000..aad6944
--- /dev/null
+++ b/records/records.gpr
@@ -0,0 +1,5 @@
+project Records is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("records.adb");
+end Records;
diff --git a/records/src/records.adb b/records/src/records.adb
new file mode 100644
index 0000000..f3c60ae
--- /dev/null
+++ b/records/src/records.adb
@@ -0,0 +1,28 @@
+with Ada.Text_IO; use Ada.Text_IO;
+
+procedure Records is
+
+  type Month_Type is (January, February, March, April, May, June, July, August,
+                      September, October, November, December);
+
+  type Date is record
+    Day   : Integer range 1 .. 31 := 1;
+    Month : Month_Type := January;
+    Year  : Integer := 1970;
+  end record;
+
+  function To_String (D : Date) return String is
+  begin
+    return Month_Type'Image (D.Month) & " " & Integer'Image (D.Day) & ", " &
+      Integer'Image(D.Year);
+  end To_String;
+
+  Epoch : Date;
+  Ada_Birthday : Date := (10, December, 1815);
+  Leap_Day_2020 : Date := (29, February, 2020);
+
+begin
+  Put_Line ("Epoch is " & To_String (Epoch));
+  Put_Line ("Ada's birthday is " & To_String (Ada_Birthday));
+  Put_Line ("Leap day 2020: " & To_String (Leap_Day_2020));
+end Records;
diff --git a/ring_buffer/ring_buffer.gpr b/ring_buffer/ring_buffer.gpr
new file mode 100644
index 0000000..bac706f
--- /dev/null
+++ b/ring_buffer/ring_buffer.gpr
@@ -0,0 +1,5 @@
+project Ring_Buffer is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("ring_buffer.adb");
+end Ring_Buffer;
diff --git a/ring_buffer/src/ring_buffer.adb b/ring_buffer/src/ring_buffer.adb
new file mode 100644
index 0000000..500ec5c
--- /dev/null
+++ b/ring_buffer/src/ring_buffer.adb
@@ -0,0 +1,94 @@
+with Ada.Text_IO; use Ada.Text_IO;
+
+procedure Ring_Buffer is
+
+  type Natural_Array is array (Natural range <>) of Integer;
+
+  type Ring_Buffer (Capacity : Natural) is record
+    Start_Index : Natural := 0; -- TODO: somehow make these 'mod Size'.
+    Cur_Index   : Natural := 0;
+    Empty       : Boolean := True;
+    -- TODO: the index type should be 'mod Size'.
+    -- TODO: 0 .. Capacity wastes 1 slot of space.
+    Buffer      : Natural_Array (0 .. Capacity) := (others => 0);
+  end record;
+
+  function Size (RB : Ring_Buffer) return Natural is
+  begin
+    if RB.Empty then
+      return 0;
+    elsif RB.Cur_Index = RB.Start_Index then
+      return RB.Capacity;
+    else
+      return (RB.Cur_Index - RB.Start_Index) mod RB.Capacity;
+    end if;
+  end Size;
+
+  function Push (RB : in out Ring_Buffer; Value : Integer) return Boolean is
+  begin
+    if Size (RB) = RB.Capacity then
+      return False;
+    else
+      RB.Buffer (RB.Cur_Index) := Value;
+      RB.Cur_Index := (RB.Cur_Index + 1) mod RB.Capacity;
+      RB.Empty := False;
+      return True;
+    end if;
+  end Push;
+
+  procedure Push (RB : in out Ring_Buffer; Value : Integer) is
+    unused : Boolean := Push (RB, Value);
+  begin
+    return;
+  end Push;
+
+  function Pop (RB : in out Ring_Buffer; Value : out Integer) return Boolean is
+  begin
+    if Size (RB) = 0 then
+      return False;
+    else
+      Value := RB.Buffer (RB.Start_Index);
+      RB.Start_Index := (RB.Start_Index + 1) mod RB.Capacity;
+      if RB.Start_Index = RB.Cur_Index then
+        RB.Empty := True;
+      end if;
+      return True;
+    end if;
+  end Pop;
+
+  procedure Pop (RB : in out Ring_Buffer) is
+    Dummy  : Integer;
+    unused : Boolean := Pop (RB, Dummy);
+  begin
+    return;
+  end Pop;
+
+  procedure Print (RB : Ring_Buffer) is
+  begin
+    Put ("[");
+    for I in 0 .. Size (RB) - 1 loop
+      Put (Integer'Image (RB.Buffer ((RB.Start_Index + I) mod RB.Capacity)));
+    end loop;
+    Put_Line ("]");
+  end Print;
+
+  Capacity : constant Natural := 5;
+  RB : Ring_Buffer (Capacity);
+
+begin
+  Push (RB, 1);
+  Push (RB, 2);
+  Push (RB, 3);
+  Push (RB, 4);
+  Push (RB, 5);
+  -- Full!
+  Push (RB, 6);
+  Push (RB, 7);
+  -- Make some space.
+  Pop (RB);
+  Pop (RB);
+  -- Push more.
+  Push (RB, 8);
+  Push (RB, 9);
+  Print (RB);
+end Ring_Buffer;
diff --git a/stack/src/main.adb b/stack/src/main.adb
new file mode 100644
index 0000000..977a46b
--- /dev/null
+++ b/stack/src/main.adb
@@ -0,0 +1,20 @@
+with Ada.Assertions; use Ada.Assertions;
+with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;
+with Ada.Text_IO; use Ada.Text_IO;
+
+with Stack;
+
+procedure Main is
+   package IntStack is new Stack (Integer);
+   S : IntStack.Stack;
+   Val : Integer;
+begin
+   Put_Line ("Hello world!");
+   for I in 1 .. 5 loop
+      IntStack.Push (S, I);
+   end loop;
+   while not IntStack.Empty (S) loop
+      Assert (IntStack.Pop (S, Val));
+      Put_Line (Val'Image);
+   end loop;
+end Main;
diff --git a/stack/src/stack.adb b/stack/src/stack.adb
new file mode 100644
index 0000000..4dc8fb1
--- /dev/null
+++ b/stack/src/stack.adb
@@ -0,0 +1,31 @@
+with Ada.Unchecked_Deallocation;
+
+package body Stack is
+   procedure Free is new Ada.Unchecked_Deallocation (Node, Node_Access);
+
+   procedure Push (S : in out Stack; Val : T) is
+      New_Top : Node_Access := new Node;
+   begin
+      New_Top.Val := Val;
+      New_Top.Bottom := S.Top;
+      S.Top := New_Top;
+   end Push;
+
+   function Pop (S : in out Stack; Val : out T) return Boolean is
+      Old_Top : Node_Access := S.Top;
+   begin
+      if Old_Top /= null then
+         Val := Old_Top.Val;
+         S.Top := Old_Top.Bottom;
+         Free (Old_Top);
+         return True;
+      else
+         return False;
+      end if;
+   end Pop;
+
+   function Empty (S : Stack) return Boolean is
+   begin
+      return S.Top = null;
+   end Empty;
+end Stack;
diff --git a/stack/src/stack.ads b/stack/src/stack.ads
new file mode 100644
index 0000000..4f390e3
--- /dev/null
+++ b/stack/src/stack.ads
@@ -0,0 +1,26 @@
+generic
+   type T is private;
+package Stack is
+   type Stack is private;
+
+   -- Push a value into the stack.
+   procedure Push (S : in out Stack; Val : T);
+
+   -- Pop a value from the stack.
+   function Pop (S : in out Stack; Val : out T) return Boolean;
+
+   -- Return true if the stack is empty, false otherwise.
+   function Empty (S : Stack) return Boolean;
+private
+   type Node;
+   type Node_Access is access Node;
+
+   type Node is record
+      Val    : T;
+      Bottom : Node_Access;
+   end record;
+
+   type Stack is record
+      Top : Node_Access;
+   end record;
+end Stack;
diff --git a/stack/stack.gpr b/stack/stack.gpr
new file mode 100644
index 0000000..70e045c
--- /dev/null
+++ b/stack/stack.gpr
@@ -0,0 +1,5 @@
+project Stack is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("main.adb");
+end Stack;
\ No newline at end of file
diff --git a/tree/src/main.adb b/tree/src/main.adb
new file mode 100644
index 0000000..b9ece1a
--- /dev/null
+++ b/tree/src/main.adb
@@ -0,0 +1,14 @@
+with Ada.Text_IO; use Ada.Text_IO;
+
+with Tree;
+
+procedure Main is
+   package IntTree is new Tree (Integer);
+   T : IntTree.Tree_Access := new IntTree.Tree;
+begin
+   T.Left := new IntTree.Tree;
+   T.Right := new IntTree.Tree;
+   T.Right.Left := new IntTree.Tree;
+
+   Put_Line ("Tree height:" & IntTree.Height (T)'Image);
+end Main;
diff --git a/tree/src/tree.adb b/tree/src/tree.adb
new file mode 100644
index 0000000..7e4a897
--- /dev/null
+++ b/tree/src/tree.adb
@@ -0,0 +1,12 @@
+package body tree is
+
+   function Height (T : Tree_Access) return Integer is
+   begin
+      if T = null then
+         return 0;
+      else
+         return 1 + Integer'Max (Height (T.Left), Height (T.Right));
+      end if;
+   end Height;
+
+end tree;
diff --git a/tree/src/tree.ads b/tree/src/tree.ads
new file mode 100644
index 0000000..1cf26fc
--- /dev/null
+++ b/tree/src/tree.ads
@@ -0,0 +1,18 @@
+generic
+   type T is private;
+
+package tree is
+
+   type Tree;
+   type Tree_Access is access Tree;
+
+   type Tree is record
+      Val   : T;
+      Left  : Tree_Access;
+      Right : Tree_Access;
+   end record;
+
+   -- Returns the height of the tree.
+   function Height (T : Tree_Access) return Integer;
+
+end tree;
diff --git a/tree/tree.gpr b/tree/tree.gpr
new file mode 100644
index 0000000..bef680a
--- /dev/null
+++ b/tree/tree.gpr
@@ -0,0 +1,5 @@
+project Tree is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("main.adb");
+end Tree;
diff --git a/typing/src/typing.adb b/typing/src/typing.adb
new file mode 100644
index 0000000..876c5db
--- /dev/null
+++ b/typing/src/typing.adb
@@ -0,0 +1,131 @@
+with Ada.Text_IO; use Ada.Text_IO;
+
+procedure Typing is
+  -- Notes:
+  -- Every "built-in" type in Ada is defined with facilities generally available
+  -- to the user.
+
+  ------------------------------------------------------------------------------
+  -- Ranged integers.
+  ------------------------------------------------------------------------------
+  type My_Int is range -1 .. 20;
+
+  function Overflow (X : My_Int) return My_Int is
+  begin
+    return X + 1;
+  end Overflow;
+
+  procedure Test_My_Int is
+    -- N overflows.
+    --N : My_Int := Overflow (My_Int'Last);
+
+    -- C is equal to (12 + 15) / 2 = 13.
+    -- The reason C does not overflow is that type-level overflows are performed
+    -- at specific boundaries for efficiency reasons, in this case when the
+    -- result of the computation is assigned to the variable C. The value 13 is
+    -- within the range of My_Int, so we do not get an overflow exception in this
+    -- case.
+    A : My_Int := 12;
+    B : My_Int := 15;
+    C : My_Int := (A + B) / 2;
+  begin
+    for I in My_int loop
+      Put_Line (My_Int'Image (I));
+    end loop;
+
+    --Put_Line ("My_Int N = " & My_Int'Image (N));
+    Put_Line ("My_Int C = " & My_Int'Image (C));
+  end Test_My_Int;
+
+  ------------------------------------------------------------------------------
+  -- Unsigned integers / modular types.
+  ------------------------------------------------------------------------------
+  type Mod_Int is mod 5;
+
+  procedure Test_Mod_Int is
+    A : Mod_Int := 2;
+    B : Mod_Int := 4;
+    C : Mod_Int := A + B; -- C = 1. No overflow, implicit mod operation.
+  begin
+    Put_Line ("Mod_Int C = " & Mod_Int'Image (C));
+  end Test_Mod_Int;
+
+  ------------------------------------------------------------------------------
+  -- Enumerations.
+  ------------------------------------------------------------------------------
+  type Days is (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday);
+
+  procedure Test_Days is
+  begin
+    for D in Days loop
+      Put (Days'Image (D));
+      case D is
+        when Monday .. Friday => Put_Line (" -> weekday");
+        when Saturday .. Sunday => Put_Line (" -> weekend");
+      end case;
+    end loop;
+  end Test_Days;
+
+  ------------------------------------------------------------------------------
+  -- Floats with ranges.
+  ------------------------------------------------------------------------------
+  type T_Norm is new Float range -1.0 .. +1.0;
+
+  procedure Test_T_Norm is
+    A : T_Norm := 0.5;
+  begin
+    Put_Line ("A = " & T_Norm'Image (A));
+  end Test_T_Norm;
+
+  ------------------------------------------------------------------------------
+  -- Casting.
+  ------------------------------------------------------------------------------
+  type Meters is new Float;
+  type Miles is new Float;
+
+  procedure Test_Units is
+    Dist_Imperial : Miles;
+    Dist_Metric : constant Meters := 100.0;
+  begin
+    Dist_Imperial := Miles (Dist_Metric) / 1609.0;
+    Put_Line (Meters'Image (Dist_Metric) & " meters is " & Miles'Image (Dist_Imperial) & " miles");
+  end Test_Units;
+
+  ------------------------------------------------------------------------------
+  -- Derived types.
+  --
+  -- Derived types introduce a new type and usually constrain the parent type.
+  ------------------------------------------------------------------------------
+  type SSN is new Integer range 0 .. 999_99_9999;
+
+  procedure Test_SSN is
+    X : SSN := 111_22_3333;
+  begin
+    Put_Line("SSN X = " & SSN'Image (X));
+  end Test_SSN;
+
+  ------------------------------------------------------------------------------
+  -- Subtypes types.
+  --
+  -- Subtypes express constraints without introducing a new type.
+  -- Constraints are enforced at runtime.
+  ------------------------------------------------------------------------------
+  subtype Weekend_Days is Days range Saturday .. Sunday;
+
+  procedure Test_Subtypes is
+    A : Weekend_Days := Saturday;
+    B : Days := A; -- OK.
+  begin
+    Put_Line ("Day B is " & Days'Image (B));
+    --A := Monday; -- Runtime exception.
+  end Test_Subtypes;
+
+begin
+  Test_My_Int;
+  Test_Mod_Int;
+  Test_Days;
+  Test_T_Norm;
+  Test_Units;
+  Test_SSN;
+  Test_Subtypes;
+end Typing;
diff --git a/typing/typing.gpr b/typing/typing.gpr
new file mode 100644
index 0000000..fdc5051
--- /dev/null
+++ b/typing/typing.gpr
@@ -0,0 +1,5 @@
+project Typing is
+    for Source_Dirs use ("src");
+    for Object_Dir use "obj";
+    for Main use ("typing.adb");
+end Typing;