what is the use of over loaded functions.

**Mark Rae [MVP]** · Jul 30 '07, 12:15 PM

Re: what is the use of over loaded functions.

<veebhudhi.chan dramouli@gmail. comwrote in message
news:1185796426 .667869.128470@ i38g2000prf.goo glegroups.com.. .

Instead of using same name i can use different name,

True, but then it's not the same function...:-)

is there any specific purpous is there to define the polymorphic
overloaded functions in c#

It allows you to define different "versions" of the same function with
different signatures - other languages did something similar with optional
parameters, but C# doesn't, thank God!

http://www.csharpfriends.com/Articles/getArticle.aspx?articleID=105

--
Mark Rae
ASP.NET MVP

Mark Rae - JavaScript Disabled

http://www.markrae.net

**Jon Skeet [C# MVP]** · Jul 30 '07, 12:25 PM

Re: what is the use of over loaded functions.

On Jul 30, 12:53 pm, veebhudhi.chand ramo...@gmail.c om wrote:

Instead of using same name i can use different name,
is there any specific purpous is there to define the polymorphic
overloaded functions in c#

For constructors, you can't change the name to start with.
For everything else - it's just more convenient not to have to create
lots of different method names.

Look at the overloads for Console.WriteLi ne, for example - would you
really want that many different method names?

Jon

**Hitesh Ashar** · Jul 30 '07, 12:45 PM

Re: what is the use of over loaded functions.

One use of overloaded is to provide default parameter values.

Consider a function that takes three parameters with one parameter being
the same for 90% of the calls.
You could overload that function with one that takes two parameters and
delegate the call to your original function providing the third value
yourself.

My 2c.

veebhudhi.chand ramouli@gmail.c om wrote:

Instead of using same name i can use different name,
is there any specific purpous is there to define the polymorphic
overloaded functions in c#
>

--
Hitesh Ashar
hitesh (at) asharism (dot) com

**Paul Werkowitz** · Jul 30 '07, 12:45 PM

Re: what is the use of over loaded functions.

Am Mon, 30 Jul 2007 13:02:26 +0100 schrieb Mark Rae [MVP]:

>
It allows you to define different "versions" of the same function with
different signatures - other languages did something similar with optional
parameters, but C# doesn't, thank God!
>

Optional parameters:
Why do you prefer

void f ( int data )
void f ( int data, bool withLogging )
over

void f( int data, bool withLogging = false )

???

**Mark Rae [MVP]** · Jul 30 '07, 01:25 PM

Re: what is the use of over loaded functions.

"Paul Werkowitz" <newsgroups@pri maprogramm.dewr ote in message
news:1tq0rqqgu7 n5q$.1pmlifo0vd 6il$.dlg@40tude .net...

void f( int data, bool withLogging = false )

That isn't an optional parameter - it's a parameter with a default value...

Not the same thing at all!

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ASP.NET MVP

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http://www.markrae.net

**Jon Skeet [C# MVP]** · Jul 30 '07, 01:35 PM

Re: what is the use of over loaded functions.

On Jul 30, 2:19 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

void f( int data, bool withLogging = false )

>
That isn't an optional parameter - it's a parameter with a default value...
>
Not the same thing at all!

I certainly see the two as being equivalent. There's no point in
having a default value unless the parameter is optional, and if it's
optional then surely it needs a default value.

What's the practical difference between the two in your view?

Jon

**Mark Rae [MVP]** · Jul 30 '07, 02:55 PM

Re: what is the use of over loaded functions.

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1185802100 .956957.105850@ r34g2000hsd.goo glegroups.com.. .

On Jul 30, 2:19 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

void f( int data, bool withLogging = false )

>>
>That isn't an optional parameter - it's a parameter with a default
>value...
>>
>Not the same thing at all!

>
I certainly see the two as being equivalent. There's no point in
having a default value unless the parameter is optional, and if it's
optional then surely it needs a default value.
>
What's the practical difference between the two in your view?

There's no practical difference, but an optional parameter (certainly in the
VB utilisation) doesn't actually have to exist...

--
Mark Rae
ASP.NET MVP

Mark Rae - JavaScript Disabled

http://www.markrae.net

**Jon Skeet [C# MVP]** · Jul 30 '07, 03:15 PM

Re: what is the use of over loaded functions.

On Jul 30, 3:42 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

What's the practical difference between the two in your view?

>
There's no practical difference, but an optional parameter (certainly in the
VB utilisation) doesn't actually have to exist...

What exactly does that mean? What does a parameter which doesn't exist
look like?

Jon

**Mark Rae [MVP]** · Jul 30 '07, 03:25 PM

Re: what is the use of over loaded functions.

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1185808485 .122284.163490@ 57g2000hsv.goog legroups.com...

On Jul 30, 3:42 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

>>What's the practical difference between the two in your view?

>>
>There's no practical difference, but an optional parameter (certainly in
>the
>VB utilisation) doesn't actually have to exist...

>
What exactly does that mean? What does a parameter which doesn't exist
look like?

Private Sub Draw(Optional X As Variant, Optional Y As Variant)
If IsMissing(X) Then X = 720
If IsMissing(Y) Then Y = 2880
Cls
Circle (X, Y), 700
End Sub

Draw()
Draw(600)
Draw(600, 1500)

--
Mark Rae
ASP.NET MVP

Mark Rae - JavaScript Disabled

http://www.markrae.net

**Jon Skeet [C# MVP]** · Jul 30 '07, 03:45 PM

Re: what is the use of over loaded functions.

On Jul 30, 4:22 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

What exactly does that mean? What does a parameter which doesn't exist
look like?

>
Private Sub Draw(Optional X As Variant, Optional Y As Variant)
If IsMissing(X) Then X = 720
If IsMissing(Y) Then Y = 2880
Cls
Circle (X, Y), 700
End Sub
>
Draw()
Draw(600)
Draw(600, 1500)

And what does that compile to in IL? Is "IsMissing" effectively the
same as "IsNothing" or whatever the VB terminology is? Does it work
for types other than Variant?

Jon

**Mark Rae [MVP]** · Jul 30 '07, 03:45 PM

Re: what is the use of over loaded functions.

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1185809806 .767873.202510@ d55g2000hsg.goo glegroups.com.. .

And what does that compile to in IL? Is "IsMissing" effectively the
same as "IsNothing" or whatever the VB terminology is?

I have no idea - that's actually an old bit of VB code - no idea at all if
it would work in VB.NET... :-)

Does it work for types other than Variant?

It didn't in VB...

--
Mark Rae
ASP.NET MVP

Mark Rae - JavaScript Disabled

http://www.markrae.net

**Jon Skeet [C# MVP]** · Jul 30 '07, 03:55 PM

Re: what is the use of over loaded functions.

On Jul 30, 4:42 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

And what does that compile to in IL? Is "IsMissing" effectively the
same as "IsNothing" or whatever the VB terminology is?

>
I have no idea - that's actually an old bit of VB code - no idea at all if
it would work in VB.NET... :-)

Ah. Looking in MSDN for VB.NET, it specifies:

<quote>
Every optional parameter in the procedure definition must specify a
default value.
</quote>

So at least in VB.NET, they *are* the same thing after all. That's a
relief in terms of my mental model, at the very least :)

Does it work for types other than Variant?

>
It didn't in VB...

I suspect that it was just a "default default" value which was the
equivalent of Nothing, or some singleton "missing value".

Jon

**G.Doten** · Jul 30 '07, 04:25 PM

Re: what is the use of over loaded functions.

Jon Skeet [C# MVP] wrote:

On Jul 30, 4:42 pm, "Mark Rae [MVP]" <m...@markNOSPA Mrae.netwrote:

>>And what does that compile to in IL? Is "IsMissing" effectively the
>>same as "IsNothing" or whatever the VB terminology is?

>I have no idea - that's actually an old bit of VB code - no idea at all if
>it would work in VB.NET... :-)

>
Ah. Looking in MSDN for VB.NET, it specifies:
>
<quote>
Every optional parameter in the procedure definition must specify a
default value.
</quote>

Yes, in fact "optional parameter" is a misleading term. I remember a
long thread back around 2000 in this ng, back when C# was new and some
people had a real issue with C# not having VB's concept of a so-called
"optional parameter" (and, indeed, VB.NET not supporting optional
parameters a la VB6). They aren't optional parameters but are hard-coded
default values.

IIRC, they are not fun to use because they are like a C# public const
variable vs. a readonly variable. With the former, the const value is
actually pulled out of the referenced assembly and inserted directly
into the consuming assembly; with the latter, a reference to the
readonly variable is deposited into the consuming assembly. Why is this
important. Well if you set your const to 12 and then change it to 13
then each and every assembly that references that public const must then
be recompiled to get the new 13 value. VB.NET's so-called optional
parameters work the same way. Avoid them! :-)

Here's what I could find with Google.

Real optional params (i.e., much of what has been discussed again in
this thread and real optional parameters with C#'s params keyword):

http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/browse_thread/thread/6d5408048cb87ae/4be95c94bf945e2d?lnk=gst&q=vb+optional+parameter+default+hard-coded&rnum=1#4be95c94bf945e2d

Pointed to from a thread in this ng - calling COM objects that have
optional parameters:

Error - Office.com

http://support.microsoft.com/default.aspx?scid=kb;en-us;305814

And I joined in the fray here:

http://groups.google.com/group/microsoft.public.dotnet.languages.csharp/browse_thread/thread/4113cbd4a63e1760/fbfa58605ebd935e?lnk=gst&q=vb+optional+parameter+default+glenn&rnum=1#fbfa58605ebd935e

Lastly, another thread I just read points out that VB.NET optional
parameters are not CLS-compliant so, for example, an optional parameter
to a VB.NET method would only be optional to other VB.NET code, to C#
and other non-VB.NET languages the parameter would not be optional.

HTH.

--
-glenn-

**Mark Rae [MVP]** · Jul 30 '07, 05:05 PM

Re: what is the use of over loaded functions.

"Jon Skeet [C# MVP]" <skeet@pobox.co mwrote in message
news:1185810806 .017311.22110@w 3g2000hsg.googl egroups.com...

And what does that compile to in IL? Is "IsMissing" effectively the
same as "IsNothing" or whatever the VB terminology is?

>>
>I have no idea - that's actually an old bit of VB code - no idea at all
>if
>it would work in VB.NET... :-)

>
Ah. Looking in MSDN for VB.NET, it specifies:
>
<quote>
Every optional parameter in the procedure definition must specify a
default value.
</quote>
>
So at least in VB.NET, they *are* the same thing after all. That's a
relief in terms of my mental model, at the very least :)

I couldn't agree more! I always hated that whole VB "sloppiness "...

Does it work for types other than Variant?

>>
>It didn't in VB...

>
I suspect that it was just a "default default" value which was the
equivalent of Nothing, or some singleton "missing value".

No doubt.

--
Mark Rae
ASP.NET MVP

Mark Rae - JavaScript Disabled

http://www.markrae.net

what is the use of over loaded functions.

what is the use of over loaded functions.

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