//                                   
//                                   
// -$@:@                      @@     
// @  -@   @                   @     
// $:     @@@@@   $@$:   $@+@  @ @@@ 
// -$@$    @        -@  $+ -@  @ *$  
//    *$   @     -$@$@  @      @$$   
//     @   @     $*  @  @      @$$   
// @+ -$   @: :$ @- *@  $* -$  @ -$  
// @:@$-   :@@$- -$$-@@  $@$- @@ @@@-
//                                   
//                                   
//                                   
//                                   

type Stack {
  Stack push(Any x);
  <Stack, Any> pop();
  void foreach(Any -> void);
}

class ListStackC(List list) : Stack impl Stack {

  Stack push(Any x) {
    return new ListStackC(list = new ConsList(car = x, cdr = list));
  }

  <Stack, Any> pop() {
    return (new ListStackC(list = list.rest()), list.first());
  }

  void foreach(Any -> void f) { list.foreach(f); }

  export Stack : push, pop, foreach;
}

Stack emptyStack() {
  return new ListStackC(list = new MTList());
}

//                                                                                    
//                                                                                    
//@@@@@:                          @@            @@  -$@:@                      @@     
// @  :@                           @             @  @  -@   @                   @     
// @  -$   $@$  @@  @@ @@:@@:   $@:@  -@@$    $@:@  $:     @@@@@   $@$:   $@+@  @ @@@ 
// @@@$   $- -$  @   @  @+ :@  $* *@  $  -$  $* *@  -$@$    @        -@  $+ -@  @ *$  
// @  :$  @   @  @   @  @   @  @   @  @@@@@  @   @     *$   @     -$@$@  @      @$$   
// @   @  @   @  @   @  @   @  @   @  $      @   @      @   @     $*  @  @      @$$   
// @  :@  $- -$  @: +@  @   @  $* *@  +:     $* *@  @+ -$   @: :$ @- *@  $* -$  @ -$  
//@@@@@:   $@$   :@$-@@@@@ @@@  $@:@@  $@@+   $@:@@ @:@$-   :@@$- -$$-@@  $@$- @@ @@@-
//                                                                                    
//                                                                                    
//                                                                                    
//                                                                                    

type BoundedStack <: Stack {
  BoundedStack push(Any x);
  <BoundedStack, Any> pop();
  bool isFull();
  int spaceRemaining();
}

// space = number of pushes possible on this stack
class BoundedStackC(Stack stack, int space) : BoundedStack impl BoundedStack {

  bool isFull() { return space < 1; }
  int spaceRemaining() { return space; }

  BoundedStack push(Any x) {
    if(isFull()) { error("Stack is full"); }
    else {
      return new BoundedStackC(stack = stack.push(x), space = space - 1);
    };
  }

  <BoundedStack, Any> pop() {
    (Stack s, Any obj) = stack.pop();
    return (new BoundedStackC(stack = s, space = space + 1), obj);
  }

  void foreach(Any -> void f) { stack.foreach(f); }

  export BoundedStack : push, pop, isFull, spaceRemaining, foreach;
}

BoundedStack emptyBoundedStack(int n) {
  return new BoundedStackC(stack = emptyStack(), space = n);
}

//                                                 
//                                                 
// +@@@*                                           
//   @            @                                
//   @   @@:@@:  @@@@@  -@@$    $@-@@ -@@$   @@-$+ 
//   @    @+ :@   @     $  -$  $* :@  $  -$   @$ : 
//   @    @   @   @     @@@@@  @   @  @@@@@   @    
//   @    @   @   @     $      @   @  $       @    
//   @    @   @   @: :$ +:     $* :@  +:      @    
// -@@@: @@@ @@@  :@@$-  $@@+   $@:@   $@@+  @@@@@ 
//                                -$               
//                             -@@$                
//                                                 
//                                                 

struct IntegerC(int value) : Integer { }

//                            
//                            
// @@@      @                 
//  @                    @    
//  @     -@@    :@@+@  @@@@@ 
//  @       @    @$ -@   @    
//  @       @    :@@$-   @    
//  @  @    @       *@   @    
//  @  @    @    @  :@   @: :$
// @@@@@  @@@@@  $+@@:   :@@$-
//                            
//                            
//                            
//                            

type List {

  List addToFront(Any);
  List addToEnd(Any);

  Any  first();
  Any  atIndex(int);
  Any  last();

  List rest();
  List drop(int);
  List take(int);

  List appendToEnd(List);
  List appendToFront(List);

  List reverse();

  int length();
  bool empty();

  List map(Any -> Any);
  Any  foldl(<Any, Any> -> Any, Any);
  Any  foldr(<Any, Any> -> Any, Any);
  List filter(Any -> bool);
  void foreach(Any -> void);

}

class MTList() : List impl List {

  List add(Any elt) {
    return new ConsList(car = elt, cdr = (this : List));
  }

  Any no_elts(int n) {
    error("The empty list has no elements!");
  }

  Any no_elt() {
    error("The empty list has no elements!");
  }

  List rest() {
    error("Cannot get the rest of the empty list!");
  }

  List drop(int n) {
    if n == 0 {
      this : List;
    } else {
      error("Attempt to drop elements from an empty list!");
    };
  }

  List take(int n) {
    if n == 0 {
      this : List;
    } else {
      error("Attempt to take elements from an empty list!");
    };
  }

  List ret_other(List l) { return l; }

  List reverse() { return (this : List); }

  int length() { return 0; }

  bool empty() { return true; }

  List map(Any -> Any f) { return (this : List); }

  Any fold(<Any, Any> -> Any f, Any i) { return i; }

  List filter(Any -> bool f) { return (this : List); }

  void foreach(Any -> void f) { return(); }

  export List : add as addToFront, add as addToEnd,
                no_elt as first, no_elts as atIndex, no_elt as last,
                rest, drop, take, reverse,
                ret_other as  appendToEnd, ret_other as appendToFront,
                length, empty,
                map, fold as foldl, fold as foldr, filter, foreach;
}

// Since init slots get translated to init fields by need, we can put
// car and cdr here, and then use them appropriately inside the methods
// which will make them fields.
class ConsList(Any car, List cdr) : List impl List {

  Any first() { return car; }

  Any atIndex(int n) {
    if n == 0 {
      car;
    } else {
      cdr.atIndex(n - 1);
    };
  }

  Any last() {
    if cdr.empty() {
      car;
    } else {
      cdr.last();
    };
  }

  List rest() {
    return cdr;
  }

  List drop(int n) {
    if n == 0 {
      this : List;
    } else {
      cdr.drop(n - 1);
    };
  }

  List take(int n) {
    if n == 0 {
      new MTList();
    } else {
      new ConsList(car = car, cdr = cdr.take(n - 1));
    };
  }

  List addToFront(Any x) {
    return new ConsList(car = x, cdr = (this : List));
  }

  List addToEnd(Any x) {
    return new ConsList(car = car, cdr = cdr.addToEnd(x));
  }

  List appendToFront(List other) {
    if other.empty() {
      this : List;
    } else {
      new ConsList(car = other.first(), cdr = other.drop(1));
    };
  }

  List appendToEnd(List other) {
    return new ConsList(car = car, cdr = cdr.appendToEnd(other));
  }

  List reverse() {
    return cdr.reverse().addToEnd(car);
  }

  int length() { return 1 + cdr.length(); }

  bool empty() { return false; }

  List map(Any -> Any f) {
    return new ConsList(car = f(car), cdr = cdr.map(f));
  }

  Any foldl(<Any, Any> -> Any f, Any i) {
    return f(car, cdr.foldl(f, i));
  }

  Any foldr(<Any, Any> -> Any f, Any i) {
    return cdr.foldr(f, f(car, i));
  }

  List filter(Any -> bool f) {
    if f(car) {
      new ConsList(car = car, cdr = cdr.filter(f));
    } else {
      cdr.filter(f);
    };
  }

  void foreach(Any -> void f) {
    f(car);
    cdr.foreach(f);
  }

  export List : addToFront, addToEnd, first, atIndex, last, reverse,
                rest, drop, take, appendToEnd, appendToFront, length, empty,
                map, foldl, foldr, filter, foreach;
}


//                                                        
//                                                        
//@@@@@@                               @@                 
// @   @                                @                 
// @ @   @@  @@   $@$: @@+-$: @@:@$-    @    -@@$   :@@+@ 
// @@@    $ -$-     -@  @+@$@  @: -$    @    $  -$  @$ -@ 
// @ @     $$-   -$@$@  @ @ @  @   @    @    @@@@@  :@@$- 
// @      -$$    $*  @  @ @ @  @   @    @    $         *@ 
// @   @ -$- $   @- *@  @ @ @  @: -$    @    +:     @  :@ 
//@@@@@@ @@  @@  -$$-@@@@@@@@@ @-@$   @@@@@   $@@+  $+@@: 
//                             @                          
//                            @@@                         
//                                                        
//                                                        


// Stack empty = emptyBoundedStack(5);
// Stack s1 = empty.push(new IntegerC(value = 5));
// Stack s2 = s1.push(new IntegerC(value = 3));
// Stack s3 = s2.push(new IntegerC(value = 10));
// Stack s4 = s3.push(new IntegerC(value = 20));
// Stack s5 = s4.push(new IntegerC(value = 40));

// use foreach + don't care(about binding) syntax

// _ = s5.foreach(void fun(Any x) {
//                  cond {
//                    x isa Integer => printLine(intToString((x : Integer).value));
//                    else             printLine("Unknown type of value");
//                  };
//                });

// Now try adding something to s5!

// Stack s6 = s5.push(new IntegerC(value = 50));