/* polymorphic linked lists with a mixture of generics and inheritance */
using System;

// want: linked list with both natural and ad-hoc polymorphic functions

public interface addable<T>
{
   T add(T other);
}

public class integer : addable<integer>
{
   internal int x; // internal means public within same assembly
   public integer(int y) {x=y;} // constructor
   public integer add(integer other) { return new integer(other.x+x); }
   public override string ToString() { return ""+x; }
}

public class rational : addable<rational>
{
   internal int n, d;  // numerator and denominator
   public rational(int a, int b) { n=a;  d=b; }
   public rational add(rational R)
   {  int sd = R.d * d;
      int sn = n*R.d + R.n*d;
      return new rational(sn,sd);
   }
   public override string ToString() { return n+"/"+d; }
}


// polymorphic linked list class
public class cell<T> where T : addable<T>
{
  internal T car;
  internal cell<T> cdr;
  public cell(T a, cell<T> b) {car=a;  cdr=b;} // constructor

  // naturally polymorphic function:
  public int length()
  { int ax = 0; 
    for(cell<T> i=this; i!=null; i=i.cdr) ax++;
    return ax;
  }
  
  // ad-hoc polymorphic function
  public T sum()
  {
     T ax = car;
     for(cell<T> i=cdr; i!=null; i=i.cdr) ax = ax.add(i.car);
     return ax;
  }
}// cell<T>

public class polylists
{
  public static void Main()
  {
     cell<integer> ilist = new cell<integer>(new integer(3),null);
     cell<rational> rlist = new cell<rational>(new rational(1,4),null);
     Console.WriteLine(ilist.length());
     Console.WriteLine(rlist.length());     
  }
}

// compile to .exe with (csc) mcs polylists.cs  
// disassemble into .Net IL with: monodis polylists.exe

/* generated .Net intermediate language (.Net byte code) 
====================================================================
.assembly extern mscorlib
{
  .ver 4:0:0:0
  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 ) // .z\V.4..
}
.assembly 'polylists'
{
  .custom instance void class [mscorlib]System.Runtime.CompilerServices.RuntimeCompatibilityAttribute::'.ctor'() =  (
		01 00 01 00 54 02 16 57 72 61 70 4E 6F 6E 45 78   // ....T..WrapNonEx
		63 65 70 74 69 6F 6E 54 68 72 6F 77 73 01       ) // ceptionThrows.

  .hash algorithm 0x00008004
  .ver  0:0:0:0
}
.module polylists.exe // GUID = {C7B6D94A-2CCE-47C4-8815-D7F509240D75}


  .class interface public auto ansi abstract addable`1<T>
  {

    // method line 1
    .method public virtual hidebysig newslot abstract 
           instance default !T 'add' (!T other)  cil managed 
    {
        // Method begins at RVA 0x0
    } // end of method addable`1::add

  } // end of class addable`1

  .class public auto ansi beforefieldinit integer
  	extends [mscorlib]System.Object
  	implements class addable`1<class integer>  {
    .field  assembly  int32 x

    // method line 2
    .method public hidebysig specialname rtspecialname 
           instance default void '.ctor' (int32 y)  cil managed 
    {
        // Method begins at RVA 0x2050
	// Code size 14 (0xe)
	.maxstack 8
	IL_0000:  ldarg.0 
	IL_0001:  call instance void object::'.ctor'()
	IL_0006:  ldarg.0 
	IL_0007:  ldarg.1 
	IL_0008:  stfld int32 integer::x
	IL_000d:  ret 
    } // end of method integer::.ctor

    // method line 3
    .method public final virtual hidebysig newslot 
           instance default class integer 'add' (class integer other)  cil managed 
    {
        // Method begins at RVA 0x205f
	// Code size 19 (0x13)
	.maxstack 8
	IL_0000:  ldarg.1 
	IL_0001:  ldfld int32 integer::x
	IL_0006:  ldarg.0 
	IL_0007:  ldfld int32 integer::x
	IL_000c:  add 
	IL_000d:  newobj instance void class integer::'.ctor'(int32)
	IL_0012:  ret 
    } // end of method integer::add

    // method line 4
    .method public virtual hidebysig 
           instance default string ToString ()  cil managed 
    {
        // Method begins at RVA 0x2073
	// Code size 22 (0x16)
	.maxstack 8
	IL_0000:  ldstr ""
	IL_0005:  ldarg.0 
	IL_0006:  ldfld int32 integer::x
	IL_000b:  box [mscorlib]System.Int32
	IL_0010:  call string string::Concat(object, object)
	IL_0015:  ret 
    } // end of method integer::ToString

  } // end of class integer

  .class public auto ansi beforefieldinit rational
  	extends [mscorlib]System.Object
  	implements class addable`1<class rational>  {
    .field  assembly  int32 n
    .field  assembly  int32 d

    // method line 5
    .method public hidebysig specialname rtspecialname 
           instance default void '.ctor' (int32 a, int32 b)  cil managed 
    {
        // Method begins at RVA 0x208a
	// Code size 21 (0x15)
	.maxstack 8
	IL_0000:  ldarg.0 
	IL_0001:  call instance void object::'.ctor'()
	IL_0006:  ldarg.0 
	IL_0007:  ldarg.1 
	IL_0008:  stfld int32 rational::n
	IL_000d:  ldarg.0 
	IL_000e:  ldarg.2 
	IL_000f:  stfld int32 rational::d
	IL_0014:  ret 
    } // end of method rational::.ctor

    // method line 6
    .method public final virtual hidebysig newslot 
           instance default class rational 'add' (class rational R)  cil managed 
    {
        // Method begins at RVA 0x20a0
	// Code size 50 (0x32)
	.maxstack 3
	.locals init (
		int32	V_0,
		int32	V_1)
	IL_0000:  ldarg.1 
	IL_0001:  ldfld int32 rational::d
	IL_0006:  ldarg.0 
	IL_0007:  ldfld int32 rational::d
	IL_000c:  mul 
	IL_000d:  stloc.0 
	IL_000e:  ldarg.0 
	IL_000f:  ldfld int32 rational::n
	IL_0014:  ldarg.1 
	IL_0015:  ldfld int32 rational::d
	IL_001a:  mul 
	IL_001b:  ldarg.1 
	IL_001c:  ldfld int32 rational::n
	IL_0021:  ldarg.0 
	IL_0022:  ldfld int32 rational::d
	IL_0027:  mul 
	IL_0028:  add 
	IL_0029:  stloc.1 
	IL_002a:  ldloc.1 
	IL_002b:  ldloc.0 
	IL_002c:  newobj instance void class rational::'.ctor'(int32, int32)
	IL_0031:  ret 
    } // end of method rational::add

    // method line 7
    .method public virtual hidebysig 
           instance default string ToString ()  cil managed 
    {
        // Method begins at RVA 0x20de
	// Code size 33 (0x21)
	.maxstack 8
	IL_0000:  ldarg.0 
	IL_0001:  ldfld int32 rational::n
	IL_0006:  box [mscorlib]System.Int32
	IL_000b:  ldstr "/"
	IL_0010:  ldarg.0 
	IL_0011:  ldfld int32 rational::d
	IL_0016:  box [mscorlib]System.Int32
	IL_001b:  call string string::Concat(object, object, object)
	IL_0020:  ret 
    } // end of method rational::ToString

  } // end of class rational

  .class public auto ansi beforefieldinit cell`1<(class addable`1<!T>) T>
  	extends [mscorlib]System.Object
  {
    .field  assembly  !0 car
    .field  assembly  class cell`1<!0> cdr

    // method line 8
    .method public hidebysig specialname rtspecialname 
           instance default void '.ctor' (!T a, class cell`1<!T> b)  cil managed 
    {
        // Method begins at RVA 0x2100
	// Code size 21 (0x15)
	.maxstack 8
	IL_0000:  ldarg.0 
	IL_0001:  call instance void object::'.ctor'()
	IL_0006:  ldarg.0 
	IL_0007:  ldarg.1 
	IL_0008:  stfld !0 class cell`1<!0>::car
	IL_000d:  ldarg.0 
	IL_000e:  ldarg.2 
	IL_000f:  stfld class cell`1<!0> class cell`1<!0>::cdr
	IL_0014:  ret 
    } // end of method cell`1::.ctor

    // method line 9
    .method public hidebysig 
           instance default int32 length ()  cil managed 
    {
        // Method begins at RVA 0x2118
	// Code size 28 (0x1c)
	.maxstack 2
	.locals init (
		int32	V_0,
		class cell`1<!T>	V_1)
	IL_0000:  ldc.i4.0 
	IL_0001:  stloc.0 
	IL_0002:  ldarg.0 
	IL_0003:  stloc.1 
	IL_0004:  br IL_0014

	IL_0009:  ldloc.0 
	IL_000a:  ldc.i4.1 
	IL_000b:  add 
	IL_000c:  stloc.0 
	IL_000d:  ldloc.1 
	IL_000e:  ldfld class cell`1<!0> class cell`1<!0>::cdr
	IL_0013:  stloc.1 
	IL_0014:  ldloc.1 
	IL_0015:  brtrue IL_0009

	IL_001a:  ldloc.0 
	IL_001b:  ret 
    } // end of method cell`1::length

    // method line 10
    .method public hidebysig 
           instance default !T sum ()  cil managed 
    {
        // Method begins at RVA 0x2140
	// Code size 54 (0x36)
	.maxstack 2
	.locals init (
		!T	V_0,
		class cell`1<!T>	V_1)
	IL_0000:  ldarg.0 
	IL_0001:  ldfld !0 class cell`1<!0>::car
	IL_0006:  stloc.0 
	IL_0007:  ldarg.0 
	IL_0008:  ldfld class cell`1<!0> class cell`1<!0>::cdr
	IL_000d:  stloc.1 
	IL_000e:  br IL_002e

	IL_0013:  ldloca.s 0
	IL_0015:  ldloc.1 
	IL_0016:  ldfld !0 class cell`1<!0>::car
	IL_001b:  constrained. !0
	IL_0021:  callvirt instance !0 class addable`1<!T>::'add'(!0)
	IL_0026:  stloc.0 
	IL_0027:  ldloc.1 
	IL_0028:  ldfld class cell`1<!0> class cell`1<!0>::cdr
	IL_002d:  stloc.1 
	IL_002e:  ldloc.1 
	IL_002f:  brtrue IL_0013

	IL_0034:  ldloc.0 
	IL_0035:  ret 
    } // end of method cell`1::sum

  } // end of class cell`1

  .class public auto ansi beforefieldinit polylists
  	extends [mscorlib]System.Object
  {

    // method line 11
    .method public hidebysig specialname rtspecialname 
           instance default void '.ctor' ()  cil managed 
    {
        // Method begins at RVA 0x2182
	// Code size 7 (0x7)
	.maxstack 8
	IL_0000:  ldarg.0 
	IL_0001:  call instance void object::'.ctor'()
	IL_0006:  ret 
    } // end of method polylists::.ctor

    // method line 12
    .method public static hidebysig 
           default void Main ()  cil managed 
    {
        // Method begins at RVA 0x218c
	.entrypoint
	// Code size 50 (0x32)
	.maxstack 2
	.locals init (
		class cell`1<class integer>	V_0,
		class cell`1<class rational>	V_1)
	IL_0000:  ldc.i4.3 
	IL_0001:  newobj instance void class integer::'.ctor'(int32)
	IL_0006:  ldnull 
	IL_0007:  newobj instance void class cell`1<class integer>::'.ctor'(!0, class cell`1<!0>)
	IL_000c:  stloc.0 
	IL_000d:  ldc.i4.1 
	IL_000e:  ldc.i4.4 
	IL_000f:  newobj instance void class rational::'.ctor'(int32, int32)
	IL_0014:  ldnull 
	IL_0015:  newobj instance void class cell`1<class rational>::'.ctor'(!0, class cell`1<!0>)
	IL_001a:  stloc.1 
	IL_001b:  ldloc.0 
	IL_001c:  callvirt instance int32 class cell`1<class integer>::length()
	IL_0021:  call void class [mscorlib]System.Console::WriteLine(int32)
	IL_0026:  ldloc.1 
	IL_0027:  callvirt instance int32 class cell`1<class rational>::length()
	IL_002c:  call void class [mscorlib]System.Console::WriteLine(int32)
	IL_0031:  ret 
    } // end of method polylists::Main

  } // end of class polylists

*/