Generics limitation on .Net

[Luc Vaillant]

I need to initialise a typed parameter depending of its type in a generic
class.
I have tried to use the C++ template form as follow, but it doesn't work.
It seems to be a limitation of generics vs C++ templates.
Does anyone knows a workaround to do this ? Thx :

public class C<T>
{
private T myValue;

private void InitializeValue (out Byte value) { value = Byte.MinValue; }
private void InitializeValue (out Char value) { value = Char.MinValue; }
private void InitializeValue (out Int16 value) { value = Int16.MinValue; }
// ... and so on...
private void InitializeValue (out String value) { value = "Initial value"; }
private void InitializeValue (out Object value) { value = this; }

public C()
{
InitializeValue (out myValue);
}

// ...
}

[Luc Vaillant]

Joanna,

I felt angry because of such remarks :

- "Tell me, what are you doing that requires such super-optimised code ? Most
business applications are only really as fast as the person typing at the
keyboard"
==> My question was 'I need speed', and your answer is "Why, nobody cares
about speed ?"

- "If speed is that much of an issue, then don't write code that invokes so
much boxing"
==> That was the purpose of my question : how to avoid so much boxing ?

- "The example that you give doesn't really seem to fit the generic
programming model"
==> You first denigrate my work and experience based on an silly example
without knowing the work I'm doing and my needs

Now, I apologize if my provious message hurts you, and I sincerly thanks you
for the time you gave me answering my messages (I really think that).

Regards
Luc

"Joanna Carter [TeamB]" wrote:

"Luc Vaillant" <Lu*********@di scussions.micro soft.com> a écrit dans le
message de news: 81************* *************** **...icrosof t.com...

| Ok, I'm bored feeding the troll...

I'm sorry you feel that way. I have never "trolled" newsgroups; had I done
so, I doubt that I would have been appointed as a newsgroup mediator for
Borland. You obviously have a problem with people who don't give you advice
or don't have opinions with which you agree.

| With your "years of experience in OO", you should felt that answer :

Hey, I am officially on holiday for Christmas. Just because I don't come up
with the right answer first time, doesn't give you the right to denegrate my
experience. If I don't understand your question fully the first ime around,
it may be that I am working on more than just solving your problems; like
writing articles for people that do appreciate the time and effort that goes
into trying to help others understand some pretty complicated stuff.

| Have you ever written or used generics ? Is Generics just a search/replace
| tool for you ?
|
| "In addition to type safety, generic collection types generally perform
| better for storing and manipulating value types because there is no need
to
| box the value types." taken from
|
"ms-help://MS.VSCC.v80/MS.MSDN.v80/MS.VisualStudio .v80.en/dv_fxfund/html/6b90f9c3-eee3-4cd1-98d6-82019c83a1df.ht m"
:

It seems it takes a troll to think they have found an other troll :-) I find
your attitude to be insulting.

So, does the IComparer solve your problem ?

Have a peaceful New Year.

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer

[Joanna Carter [TeamB]]

"Luc Vaillant" <Lu*********@di scussions.micro soft.com> a écrit dans le
message de news: C2************* *************** **...icrosof t.com...

| Now, I apologize if my provious message hurts you, and I sincerly thanks
you
| for the time you gave me answering my messages (I really think that).

De rien :-)

Joanna

--
Joanna Carter [TeamB]
Consultant Software Engineer

[Jay B. Harlow [MVP - Outlook]]

In the context of the OPs question: I would stay with the cast over convert,
as Convert.ChangeT ype "requires" the class implement IConvertible, or at the
very least Convert.ChangeT ype needs to know the conversion.

The cast doesn't care what the value implements...

--
Hope this helps
Jay [MVP - Outlook]
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net
"Joanna Carter [TeamB]" <jo****@not.for .spam> wrote in message
news:en******** ******@TK2MSFTN GP11.phx.gbl...
| "Jay B. Harlow [MVP - Outlook]" <Ja************ @tsbradley.net> a écrit
dans
| le message de news: OQ************* **@TK2MSFTNGP15 .phx.gbl...
|
|| You need to cast to object first, as Char to T is not defined. Without a
|| constraint only object to/from T is defined.
||
||| valueType = (T)(object)Char .MinValue;
|
| You can also use the Convert class :
|
| T value = (T) Convert.ChangeT ype(Char.MinVal ue, typeof(T))
|
| Joanna
|
| --
| Joanna Carter [TeamB]
| Consultant Software Engineer
|
|

[Jay B. Harlow [MVP - Outlook]]

| 1) How do I initialize a T value without doing boxing/unboxing ?

| Not possible, must use T value = (T)(Object)cons tant value
| even if I know that the constant value if of type T
Boxes the value! Remember (object) says to box value types!

You have two options on initializing T values without boxing:

1. default(T)
2. Parameterized constructor

NOTE: The reflection trick I showed earlier will box values.

| 2) How do I compare two T values without boxing/unboxing ?
Constrain T by IComparable<T>

http://msdn2.microsoft.com/en-us/library/4d7sx9hd.aspx

NOTE: System.ICompara ble<T> is different then System.ICompara ble!

In the case of simple equality, I would recommend constraining T by
IEquatable<T>.

http://msdn2.microsoft.com/en-us/lib...US,VS.80).aspx

--
Hope this helps
Jay [MVP - Outlook]
..NET Application Architect, Enthusiast, & Evangelist
T.S. Bradley - http://www.tsbradley.net
"Luc Vaillant" <Lu*********@di scussions.micro soft.com> wrote in message
news:33******** *************** ***********@mic rosoft.com...
| Is that an answer ?
|
| I'm not writing a keyboard typing application, and I DO CARE ABOUT SPEED.
|
| > If speed is that much of an issue, then don't write code that invokes so
| > much boxing
|
| That's why I wanted to use Generics...
|
| > The example that you give doesn't really seem to fit the
| > generic programming model due to the possible differences in behaviour
| > required by the different types that may be used
|
| The example I gave was just to demonstrate the initialization issue. It
was
| not a real use case...
| Same remark about the 'Generics limitation' post I sent today. The example
| is to desmonstrate the != operator issue with generics, and this is not my
| real program...
|
| Why don't you try to answer my questions instead of explaining me that
most
| programs don't need speed, and that my examples don't "really seem to fit
the
| generic programming model".
|
| My questions are simple:
|
| 1) How do I initialize a T value without doing boxing/unboxing ?
|
| The answer is:
| Not possible, must use T value = (T)(Object)cons tant value
| even if I know that the constant value if of type T
|
| 2) How do I compare two T values without boxing/unboxing ?
|
| The answer is:
| Not possible from the answers I got in this post
|
|
| Regards
| Luc
|
|
| "Joanna Carter [TeamB]" wrote:
|
| > "Luc Vaillant" <Lu*********@di scussions.micro soft.com> a écrit dans le
| > message de news: 7F************* *************** **...icrosof t.com...
| >
| > | This will also box Char.MinValue into Object
| >
| > I won't deny that :-)
| >
| > Tell me, what are you doing that requires such super-optimised code ?
Most
| > business applications are only really as fast as the person typing at
the
| > keyboard.
| >
| > If speed is that much of an issue, then don't write code that invokes so
| > much boxing. The example that you give doesn't really seem to fit the
| > generic programming model due to the possible differences in behaviour
| > required by the different types that may be used. In which case, I would
| > tend to look elsewhere for a solution; generics are only really useful
when
| > the behaviour for *all* anticipated types is *identical*.
| >
| > Joanna
| >
| > --
| > Joanna Carter [TeamB]
| > Consultant Software Engineer
| >
| >
| >