Wednesday, 5 December 2001

1
Java to C

• Wednesday, 5 December 2001
• With Donal Lafferty
• donal.lafferty_at_cs.tcd.ie

2
1st Session

• Contents
• Background
• Types overview
• Properties
• Interfaces
• Structs and Boxing
• Enumerations
• Classes
• Inheritance
• Polymorphism
• Fragile Base Class Problem
• Operator overloading
• Equivalence
• Conversions

3
My Background
www.standonguard.com
4
Blame Canada
www.standonguard.com
5
C Background

• Introducing C
• Beginners
• Colleagues
• Not going to cover all of C
• Better references exist
• www.gotdotnet.com
• Essential C
• discuss.develop.com
• Contrast with Java
• Súil Eile

6
Java Variable Types

• Types
• Built-ins
• Primitives
• Object
• String
• Variables
• Container
• Pass by value
• References assignable

7
C Types and Variables

• Variables
• Passing
• object
• Equals
• Finalize
• ToString
• GetHashCode

8
Defining Types

• Type corresponds to public operations
• class myByte
• public byte aByte
• Separating implementation from the type
  specification
• class myByteAgain
• private int aByte
• public byte getAByte() return (byte)theByte
  
• public void setAByte(byte value)
• theByte (int)value
• Using a programming idiom has drawbacks
• 8 tokens ? 37
• Compiler support

9
Properties

• Defining C properties
• public class myByte
• private int data
• public byte Data get return (byte)data
• set data (int) value
• Accessing like a field
• myByte aByte new testByte()
• testByte.Data 2
• Useful?
• Flexible
• public class UART
• private byte data
• public byte BaudRate set data value

10
Defining Interface Types

• Separate type and implementation
• Java simulates fields with a programming idiom
• interface myByteInterface
• byte getData()
• void setData(byte value)
• C simulates fields with properties
• interface IZeroByte
• byte Data get

11
Extending and Hiding Interfaces

• Extending interfaces
• interface IByte IZeroByte
• new byte Data get set
• Implementing an interface implicitly
• public class myByte IZeroByte
• public byte Data get return (byte)0
• Implementing an interface explicitly
• interface IA
• void F()
• void F(string someArg)
• class A IA
• void IA.F() F("default") // Error!
• void IA.F(string someArg)
• Console.WriteLine("Here we go with "
  someArg)

12
Implementing Multiple Interfaces

• Implementing multiple interfaces
• public class myByte_3 IByte
• private int data
• byte IByte.Data get return (byte)data
• set data (int) value
• // IByte requires that we define the
• byte IZeroByte.Data get return (byte) 0
  
• Using the results
• static void Main()
• myByte_3 ObjectReference new
  myByte_3()
• IZeroByte IZeroReference
  ObjectReference
• byte zeroValue
  IZeroReference.Data
• IByte IByteReference
  ObjectReference
• IByteReference.Data
  (byte)(ZeroValue 1)
• byte finalValue ObjectReference.Data //
  error!

13
Type Based Operators

• as
• static void Main()
• myByte ObjectReference2 new myByte()
• // myByte does not implement IBytes
• // resulting IByteReference is a null reference
• IByte IByteReference2 ObjectReference2
  as IByte
• is
• static void Main(string args)
• myByte ObjectReference3 new myByte()
• // Manual implementation of as using is
  operation
• IByte IByteReference3 null
• if ( ObjectReference2 is IByte)
• IByteReference3 (IByte)ObjectReference2

14
Basic Structs

• User-defined value type
• Definition
• public struct SimpleByte
• public byte ByteData
• Behaves like value-type
• SimpleByte simpleSrc
• simpleSrc.ByteData 1 // this is okay
• SimpleByte simpleDest simpleSrc

15
Structs with Constructors

• Constructors semantics
• No defaults
• public struct CTORByte
• public byte ByteData
• public CTORByte (byte data)
• ByteData data
• Assignment via parameterised constructor
• Zeroed
• No access before assignment
• CTORByte CTORAssign new CTORByte(3)

16
Interfaces and Efficiency with Structs

• Implementing interfaces
• sealed
• interface IDec void Dec()
• public struct BetterByte IDec
• public byte ByteData
• public void Dec () ByteData - 1
• public void Inc () ByteData 1
• Efficiency
• Footprint
• Allocation
• / A memory light array /
• SimpleByte smallArray new SimpleByte8

17
Boxing

• Scenarios
• Collection, interfaces
• Boxing example
• BetterByte beforeBoxing
• beforeBoxing.ByteData 1
• IDec boxedByte (IDec)beforeBoxing
• boxedByte.Dec()

beforeBoxing
0
beforeBoxing
1
boxedByte
BetterByte object ByteData
IDec ref
1
18
Unboxing

• Unboxing scenario
• BetterByte unboxedByte (BetterByte)boxedByte
• unboxedByte.Dec()

boxedByte
BetterByte object ByteData
IDec ref
0
19
Enumerations

• Types
• enum Weekdays Sun, Mon, Tue, Wed, Thu, Fri, Sat
  
• enum Nibble byte Eight 8, Four 4, Two
  2,
• One 1, one 1
• Conversions
• Nibble myBinData (Nibble)12
• Nibble myBinData (byte)12
• byte byteData myBinData // Error!
• Values
• myBinData Nibble.Eight Nibble.Four //
  Assign 12
• Java
• final static

20
Inheritance

• Base class
• public class SmallByte
• public byte ByteData
• public SmallByte (byte data) ByteData data
  
• Derived class
• public class DoubleByte SmallByte
• public SmallByte SecondByte
• public DoubleByte(byte first, byte second
  )base(first)
• SecondByte new SmallByte(second)
• public DoubleByte(byte first) this (first,
  first)
• Demo
• DoubleByte srcByte new DoubleByte(3)
• SmallByte destByte srcByte
• DoubleByte secondSrc new DoubleByte(1,2)
• object thirdSrc secondSrc

21
Polymorphism in Java

• Base class
• public class Fruit
• public String Colour() return "You tell me"
• public String Shape() return "Not sure"
• Derived class
• public class Orange extends Fruit
• public String Colour() return "Orange"
• public String Shape() return "Round"
• Use
• Fruit someFruit new Fruit()
• string a someFruit.Colour() // "You tell
  me"
• string b someFruit.Shape() // "Not sure"
• someFruit new Orange()
• string c someFruit.Colour() // "Orange"
• string d someFruit.Shape() // "Round"

22
Static and Dynamic Binding in C

• Base class
• public class Fruit
• public string Colour() return "You tell me"
• public virtual string Shape() return "Not
  sure"
• Derived class
• public class Orange Fruit
• public new string Colour() return "Orange"
• public override string Shape() return
  "Round"
• Use
• Fruit someFruit new Fruit()
• string a someFruit.Colour() // "You tell
  me"
• string b someFruit.Shape() // "Not sure"
• someFruit new Orange()
• string c someFruit.Colour() // "You tell
  me"
• string d someFruit.Shape() // Round" lt--
  Good

23
Fragile Base Class

• Base class becomes dependent on derived class

Method B
Method C
Base Class
Method A
Method C '
Derived Class
24
Java Example

• Base class
• public class Fruit
• public int size
• public Fruit(int size) this.size size
• public void Resize(int size)
  this.ChangeSize(size)
• public void ChangeSize(int size) this.size
  size
• Derived class
• public class Banana extends Fruit
• public Banana(int size) super(size)
• public void Eat() this.Resize(-1)
• public void ChangeSize(int size) this.size
  size
• Use
• Banana lunch new Banana( 10 )
• System.out.println("Size" (lunch.size)) //
  Size 10
• lunch.Eat()
• System.out.println("Size" (lunch.size)) //
  Size -1

25
C Solution

• Base class
• public class Fruit
• public int size
• public Fruit(int size) this.size size
• public virtual void Resize(int size)
• this.ChangeSize(size)
• public virtual void ChangeSize(int
  size)this.sizesize
• Derived class
• public class Banana Fruit
• public Banana(int size) base(size)
• public virtual void Eat() this.Resize(-1)
• public virtual void ChangeSize(int size)
• this.size size
• Use
• Applied when variables dynamic type is or
  inherits from Banana.
• Banana lunch new Banana( 10 )
• Console.WriteLine( "Size0",lunch.size) //
  Size10

26
Pass by Reference

• ref and out
• public class IntFuncs
• static public void Zero(int data) data 0
• static public void Zero(out int data) data
  0
• static public void Inc(int data) data 1
• static public void Inc(ref int data) data
  1
• Demo
• int temp
• IntFuncs.Zero(temp) // Error! Unassigned
  variable
• IntFuncs.Zero(out temp) // temp set to 0
• IntFuncs.Inc(temp) // temp still 0
• IntFuncs.Inc(ref temp) // temp now 1

27
Basic Operator Overloading

• Customizing and /
• public class Celsius
• private double temp
• public Celsius(double temp) this.temp temp
  
• public static Celsius operator (Celsius
  LHS,Celsius RHS)
• return new Celsius(LHS.temp RHS.temp)
• public static Celsius operator / (Celsius LHS,
  double RHS)
• return new Celsius(LHS.temp / RHS)
• Using overloads
• Celsius high new Celsius(15.0)
• Celsius low new Celsius(-10.0)
• Celsius average (high low)/2 // average
  2.5

28
Table of Operators
29
Advanced Operator Overloading

• Defining as true if either temperature is
  greater than 0.0
• Short-circuit evaluation
• if ( (low high) )
• return
• Becomes
• if ( low ) return 1
• else
• Celsius temp (low high)
• if (temp) return 1
• Relevant operators
• public static Celsius operator (Celsius LHS,
  Celsius RHS)
• return ( (LHS.temp gt RHS.temp) ? LHS RHS)
• public static bool operator true(Celsius c)
• return (c.temp gt 0.0)
• public static bool operator false(Celsius c)
• return (c.temp lt 0.0)

30
Equivalence in C

• Comparison operators
• public static bool operator (Celsius LHS,
  Celsius RHS)
• return (LHS.temp RHS.temp)
• public static bool operator! (Celsius LHS,
  Celsius RHS)
• return !(LHS.temp RHS.temp)
• Providing a comparison for collections
• public override bool Equals(object o)
• if (o is Celsius)
• return this (Celsius)o
• return false

31
Defining Conversions

• public class Fahrenheit
• private double temp
• public Fahrenheit(double temp)
• this.temp temp
• public static implicit operator
  Celsius(Fahrenheit source)
• double celsiusValue (source.temp -
  32)5.0/9.0
• return new Celsius(celsiusValue)
• public static explicit operator
  double(Fahrenheit source)
• return source.temp

32
Using Conversions

• Implicit conversion
• Celsius high new Celsius(15.0)
• Fahrenheit low new Fahrenheit(14)
• Celsius average (high low)/2
• Explicit conversion
• Celsius lowInCelsius new Celsius(
• ((double)low - 32.0)5.0/9.0)

33
Other keywords

• const
• public const double EuroExchange 1.27
• readonly
• internal
• internal class SterlingConverter
• public readonly double Irish
• SterlingConverter( double exchange ) Irish
  exchange
• params
• string printf(string format, params object
  vars)
• abstract
• namespace
• namespace UCD.TCD.DSG ...
• using
• using System

34
2nd Session

• Contents
• Event Model
• Delegates
• Attributes
• Synchronization
• Arrays
• Pointer types

35
Java Event Model

• Delegation Event Model
• Event type
• ListenerInterface
• Event Source
• Listener
• Adapter class

Source Object
Message
Message
Message
Listener
Listener Interface
Listener
Listener Interface
Listener
Listener Interface
36
C Event Model

• Publisher Subscriber idiom
• Event message
• Event handler delegate
• Event publisher
• Event subscriber

Event Publisher
Event Delegate
Message
Message
Message
Subscriber
Event Handler
Subscriber
Event Handler
Subscriber
Event Handler
37
Delegates

• Analogous to a C style function pointer type
• public delegate void Charge(double cash)
• Static and instance methods
• class Till
• public delegate void AddToBill(double cash)
• public void AddToReceipt(double price)
• Console.Write("Item0\n", price )
• static public void StoreTotal(double sales)
• Console.Write("Total0\n", sales )
• Delegate-type variables can be instantiated.
• Charge billUpdate
• Till checkout new Till()
• billUpdate new Charge(checkout.AddToReceipt)

38
Delegates

• Delegates can be passed as method parameters
• static public void TestRegister(Charge update)
• update(1.27)
• Demo
• Charge billUpdate
• Till checkout new Till()
• billUpdate new Charge(checkout.AddToReceipt)
• TestRegister( billUpdate )
• Result
• Item1.27

39
Multicast Delegates

• Void return type
• Charge billUpdate new Charge(checkout.AddToRecei
  pt)
• Operators to add and remove references
• // Add method reference to delegate variable
• billUpdate new Charge(Till.StoreTotal)
• billUpdate new Charge(Till.StoreTotal)
• // Make a multicast call
• billUpdate(1.27) ? checkout.AddToReceipt(1.27)
• ? Till.StoreTotal(1.27)
• ? Till.StoreTotal(1.27)
• // Remove the second method reference
• billUpdate - new Charge(Till.StoreTotal)

billUpdate checkout.AddToReciept
billUpdate checkout.AddToReciept
Till.StoreTotal Till.StoreTotal
billUpdate checkout.AddToReciept
Till.StoreTotal
40
Event Message

• Example event object class
• class PushEventArgs EventArgs
• private string cause
• public string Cause get return cause
• public PushEventArgs(string cause)
• this.cause cause

Message
41
Event Handler Delegate

• Create a delegate-type
• delegate void PushEventHandler(
• object source,
• PushEventArgs e)

Event Delegate
Event Handler
42
Event Publisher

• Fire alarm
• class FireAlarm
• public event PushEventHandler OnPushHandler
• protected void OnPush(PushEventArgs e)
• if (OnPushHandler ! null)
• OnPushHandler(this, e)
• public void TestFireAlarm()
• OnPush(new PushEventArgs("Just a fire drill")
  )

43
Event Subscriber

• Create listener class that implements the
  call-back method
• Recall the delegate type
• delegate void PushEventHandler(object source,
  PushEventArgs e)
• Alarm bell
• class AlarmBell
• public void RingBell(object source,
  PushEventArgs e)
• Console.WriteLine (e.Cause )

44
Registering an Event Handler

• Create an event publisher
• FireAlarm publisher new FireAlarm()
• Create an event subscriber
• AlarmBell subscriber new AlarmBell()
• Create an event handler delegate
• PushEventHandler pushHandler
• pushHandlernew PushEventHandler(subscriber.RingBe
  ll)
• Register the event listener with the event
  source.
• publisher.OnPushHandler pushHandler
• Kick off a same event.
• publisher.TestFireAlarm()

45
Event Modifier and Caveats

• Event modifier splits access rights
• publisher.OnPushHandler() // Error!
• publisher.OnPushHandler pushHandler// Error!
• Also
• Delegates not in CLR
• add_OnPushHandler
• remove_OnPushHandler
• Exceptions
• Property
• add / remove
• Call order

46
Introducing Attributes

• Custom Attributes
• To generate custom meta-data
• Ex. MyExtraMetaInformation
• Distinguished Custom Attributes
• Passive data used by compilers or CLR
• Ex. Obsolete
• Pseudo Custom Attributes
• Analogous to pragma.
• Ex. StructLayout

47
Reserved Attributes

• Sample from C
• AttributeUsage
• StructLayout
• FieldOffset
• Obsolete
• Serializable

48
Using Attributes

• Before
• public struct A_B_Struct
• public int A
• private byte b
• public byte B set b value get return
  b
• After
• Serializable, StructLayout(LayoutKind.Explicit)
• public struct A_B_Struct
• FieldOffset(0) public int A
• FieldOffset(0) private byte b
• Obsolete public byte B
• set b value get return b

49
Equivalent Byte-code

• Serializable
• .class public explicit ansi serializable sealed
• beforefieldinit A_B_Struct
• extends mscorlibSystem.ValueType
• .pack 0
• .size 0
• // end of class A_B_Struct
• Obsolete
• .property instance unsigned int8 B()
• .custom instance void mscorlib
• System.ObsoleteAttribute.ctor() ( 01
  00 00 00 )
• .set instance void AttributeStuff.A_B_Structse
  t_B(unsigned int8)
• .get instance unsigned int8 AttributeStuff.A_B_S
  tructget_B()
• // end of property A_B_StructB
• FieldOffset
• .field 0 public int32 A
• .field 0 private unsigned int8 b

50
Defining a Custom Attribute

• AttributeUsage(AttributeTargets.Struct
• AttributeTargets.Property )
• public class MakerAttribute Attribute
• private string designer
• public string Designer get return designer
  
• // Constructors define the position parameters
• public MakerAttribute(string designer)
• this.designer designer
• // Public fields define the named parameters
• public string Programmer "None"

51
Using a Custom Attribute

• Applying a custom attribute
• Maker("http//www.dsg.cs.tcd.ie/laffertd")
• public struct A_B_Struct_DL
• public int A
• private byte b
• Maker("http//www.dsg.cs.tcd.ie/laffertd",
• Programmer "DL")
• public byte B set b value
• get return b

Embedded in struct definition
Embedded in property implementation
52
Accessing a Custom Attribute

• Reflective API can instantiate custom attributes
• Type type typeof(A_B_Struct_DL)
• object arr type.GetCustomAttributes(
• typeof(MakerAttribute), true)
• if (arr.Length ! 0)
• MakerAttribute maker (MakerAttribute) arr0
• Console.WriteLine(Designer 0,\nCoder
  1",
• maker.Designer,
• maker.Programmer)
• Result
• Designer http//www.dsg.cs.tcd.ie/laffertd,
• Coder None

53
Quick Word on Exceptions

• Inherit from Exception
• public class StackException Exception
• public string ErrorMessage
• public StackException(string msg)
• ErrorMessage msg
• Try-Catch-Finally
• static void Main()
• try
• int a 2, b 0
• int c a/b
• catch (System.Exception problem)
• Console.WriteLine(problem.Message)
• Console.WriteLine("Happens if exception is
  caught.)
• finally
• Console.WriteLine("This always happens.")

54
Synchronization - Locking

• Monitors provide locking
• Associated with objects
• Synchronized regions
• Demarcated by Monitor.Entry / Monitor.Exit call
  pair
• Monitor methods
• Hoares Monitor
• public static void Enter(object obj)
• public static void Exit(object obj)
• public static bool TryEnter(object, int)

55
Synchronization Notification

• Analogous to Javas Object class methods
• public final void notify()
• public final void notifyAll()
• public final void wait()
• throws InterruptedException
• Monitor class notification operations
• public static void Wait(Object obj)
• Forces thread to sleep until monitor pulsed.
• public static void Pulse(Object obj)
• Wakes first waiting thread, does not release
  monitor.
• public static void PulseAll(Object obj)
• Wakes all waiting threads.

56
lock Keyword

• lock defines a synchronized region
• lock( x )
• // Synchronized Region
• Maps to Monitor class
• System.Threading.Monitor.Enter(x)
• try
• ...
• finally
• System.Threading.Monitor.Exit(x)

57
Thread Synchronization

• class SynchTest
• static void Main()
• SynchTest unique new SynchTest()
• Thread other new Thread(
• new ThreadStart(unique.Lockin
  g))
• other.Start()
• unique.Locking()
• void Locking()
• for ( char c 'a' c lt'z' c )
• lock (this)
• Console.Write(c)
• Monitor.Pulse(this)
• if ( c lt 'z' ) Monitor.Wait(this)
• // Based on Essential C, pp108-110.

Synchronized Region
58
Thread Synchronization - Equivalent

• class SynchTest
• static void Main()
• SynchTest unique new SynchTest()
• Thread other new Thread(
• new ThreadStart(unique.Lockin
  g))
• other.Start()
• unique.Locking()
• void Locking()
• for ( char c 'a' c lt'z' c )
• Monitor.Enter(this)
• Console.Write(c)
• Monitor.Pulse(this)
• if ( c lt 'z' ) Monitor.Wait(this)
• Monitor.Exit(this)
• // Based on Essential C, pp108-110.

Synchronized Region
59
Threading example
Thread1
Thread2
Thread1
Running
Blocked getting lock
Monitor.Enter(Padlock)
Monitor.Enter(Padlock)
Thread1
Running
Blocked getting lock
Monitor.Pulse(Padlock)
Monitor.Enter(Padlock)
Thread2
Suspended
Monitor.Wait(Padlock)
Running
Monitor.Enter(Padlock)
60
Threading example - 2

Thread1
Thread2
Thread2
Running
Blocked getting lock
Monitor.Pulse(Padlock)
Monitor.Wait(Padlock)
Thread1
Suspended
Monitor.Wait(Padlock)
Running
Monitor.Exit(Padlock)
Thread1
Running
Monitor.Enter(Padlock)
Suspended
Monitor.Wait(Padlock)
61
Threading example - 3
Thread1
Thread2
Thread1

• Result
• aabbccddeeffgghhiijjkkllmmnnooppqqrrssttuuvvwwxxyy
  zz

Running
Blocked getting lock
Monitor.Pulse(Padlock)
Monitor.Wait(Padlock)
Thread2
Suspended
Monitor.Wait(Padlock)
Running
Monitor.Exit(Padlock)
62
Arrays

• Defining arrays
• Java can specify array type after variable or
  after type
• int ia
• int ia
• C always specifies array type after type
• int ia
• Initialising arrays
• Short hand for array initialization.
• int myArray 1, 2, 3, 4
• Java implicitly creates arrays of array
  references
• int ia 1, 2, null
• int ib new int22
• C requires explicit creation of array
  references.
• int ia new int2 1, 2, null
• int ib new int2, new int2

63
Array Manipulation

• Implicit conversion
• class a int value
• class b a
• ...
• a aObj new b2
• foreach
• int myArray 1, 2, 3, 4
• foreach ( int Value in myArray )
• Console.WriteLine("This element contains
  0",Value)

64
Multidimensional Arrays

• Jagged array
• int jaggedArrayOfInts new int3
• // triangular array.
• jaggedArrayOfInts0 new int3 1, 2, 3
• jaggedArrayOfInts1 new int2 4, 5
• jaggedArrayOfInts2 new int1 6

3
2
1
5
4
6
65
Multidimensional Arrays

• Rectangular arrays
• int, rectangularArray
• rectangularArray new int3,3 1,2,3,
• 4,5,6,
• 7,8,9
• int ValueofRow1Column2 rectangularArray1,2

0,
1,
2,
3
4
5
8
6
9
1
7
2
66
Unsafe Code

• Unsafe context
• Declare and apply operators to pointer variables
• Convert between pointers and integral types
• Take address of variables
• Definition
• Type declarations (C Language Specification,
  Section A)
• public unsafe struct Node
• public int Value
• public Node Left
• public Node Right
• Members
• public struct Node
• public int Value
• public unsafe Node Left
• public unsafe Node Right
• Code blocks

67
Unsafe context

• Independent from type
• public class A
• public unsafe virtual void F()
• public class B A
• public override void F() base.F()

68
Pointer types

• Unmanaged types
• Built-in types
• sbyte, byte, short, ushort, int, uint, long,
  ulong, char, float, double, decimal, or bool.
• Any enum-type
• Any pointer-type
• Struct-type that contains fields of
  unmanaged-types only
• operator
• byte // Pointer to byte
• char // Pointer to char
• int // Pointer to pointer to int
• int // Array of pointers to int
• void // Pointer to unknown type
• int pi, pj // NOT as int pi, pj
• Node left // User defined struct

69
Fixed vs Moveable

• Fixed
• Locals variables
• Pass by value parameters
• Pointer dereferences
• Moveable
• Array elements
• Object fields
• unsafe class Test
• static int x
• int y
• static void F(int p)
• p 1

70
Fixed operator

• unsafe class Test
• static int x
• static string foo foo
• int y
• static void F(int p) p 1
• static void F(char p)
• for (int i 0 pi ! '\0' i)
• Console.WriteLine(pi)
• static void Main()
• Test t new Test()
• Int arr new int10
• fixed (int p x) F(p)
• fixed (int p t.y) F(p)
• fixed (int p arr0) F(p)
• fixed (int p arr) F(p)
• fixed (char c foo) F(c)

71
Pointer Operations

• Pointer indirection ( )
• Access a member of a struct ( -gt )
• Index a pointer ( )
• Obtain the address of a variable ( )
• Increment and decrement ( / -- )
• Compare pointers ( / ! / lt / gt / lt / gt )
• Pointer arithmetic ( / - )
• Allocate memory from the call stack ( stackalloc
  )
• char buffer stackalloc char16
• Obtain size of unmanaged type ( sizeof )

72
References

• Books
• A Programmers Introduction to C by Eric
  Gunnerson, Apress
• Java in a Nutshell by By David Flanagan, OReilly
• Essential C, OReilly
• JDK V1.2
• Reference Manuals
• .NET documentation
• ECMA C Specification / CLS Specification
• http//www.adtools.com/CLI
• Discussion Groups
• DOTNET on discuss.develop.com