Empty Character Literal

**Paul E Collins** · Nov 17 '05, 10:24 AM

Re: Empty Character Literal

There is no "empty character literal", because every possible value
for a char type is one character long. You can have zero length
strings ("") but not zero-length characters, e.g. this will not
compile:

char ch = ''; // doesn't work

The closest you can get is a space (' ') or a null character ('\0',
ASCII zero).

P.

**Jon Skeet [C# MVP]** · Nov 17 '05, 10:24 AM

Re: Empty Character Literal

VJ <vijaybalki@yah oo.com> wrote:[color=blue]
> I have a property for a control ( source code not available) . The property
> accepts single char as value.. so I can set it to '/' or ':' or anything
> like that...At initialize of my From I want this property to be set to a
> empty literal. I am able to do this at design time using VS.NET property
> box. This works for controls created at design time, but for some controls I
> create at run-time I want to do the same at Form_load..[/color]

There's no such thing as an "empty" character, any more than there's an
"empty integer". What's the property used for? Character 0 (the "null"
character) *might* be an appropriate start value, but it's hard to say
without more information.

--
Jon Skeet - <skeet@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
If replying to the group, please do not mail me too

**Christof Nordiek** · Nov 17 '05, 10:24 AM

Re: Empty Character Literal

"VJ" <vijaybalki@yah oo.com> schrieb im Newsbeitrag
news:uPLg0BtyFH A.916@TK2MSFTNG P10.phx.gbl...[color=blue]
>
> I have a property for a control ( source code not available) . The
> property accepts single char as value.. so I can set it to '/' or ':' or
> anything like that...At initialize of my From I want this property to be
> set to a empty literal. I am able to do this at design time using VS.NET
> property box. This works for controls created at design time, but for some
> controls I create at run-time I want to do the same at Form_load..
>
> VJ
>[/color]
If you can do it with VS.NET, simply do it and check the value while
runtime.
The you know, what character it is and set it in code.

**Kevin Spencer** · Nov 17 '05, 10:24 AM

Re: Empty Character Literal

Just a technical note about this: The reason that you can have empty strings
is that a string is an array of char with a null terminator. That is, a
string is actually (in memory) one char longer than the actual string,
including the null terminator. A char, on the other hand, is not an array,
but a single char.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Ambiguity has a certain quality to it.

"Paul E Collins" <find_my_real_a ddress@CL4.org> wrote in message
news:di4djo$r06 $1@nwrdmz02.dmz .ncs.ea.ibs-infra.bt.com...[color=blue]
> There is no "empty character literal", because every possible value for a
> char type is one character long. You can have zero length strings ("") but
> not zero-length characters, e.g. this will not compile:
>
> char ch = ''; // doesn't work
>
> The closest you can get is a space (' ') or a null character ('\0', ASCII
> zero).
>
> P.
>
>[/color]

**Daniel Jin** · Nov 17 '05, 10:24 AM

Re: Empty Character Literal

that is not true.

..net strings are not null terminated. the reason why you can have an
empty string is because it's perfectly legal to have a 0-length array.

Kevin Spencer wrote:[color=blue]
> Just a technical note about this: The reason that you can have empty strings
> is that a string is an array of char with a null terminator. That is, a
> string is actually (in memory) one char longer than the actual string,
> including the null terminator. A char, on the other hand, is not an array,
> but a single char.
>
> --
> HTH,
>
> Kevin Spencer
> Microsoft MVP
> .Net Developer
> Ambiguity has a certain quality to it.
>
> "Paul E Collins" <find_my_real_a ddress@CL4.org> wrote in message
> news:di4djo$r06 $1@nwrdmz02.dmz .ncs.ea.ibs-infra.bt.com...[color=green]
> > There is no "empty character literal", because every possible value for a
> > char type is one character long. You can have zero length strings ("") but
> > not zero-length characters, e.g. this will not compile:
> >
> > char ch = ''; // doesn't work
> >
> > The closest you can get is a space (' ') or a null character ('\0', ASCII
> > zero).
> >
> > P.
> >
> >[/color][/color]

VJ · Nov 17 '05, 10:25 AM

Re: Empty Character Literal

Ok I got this one... The property had a corresponding Int property which if
I set to zero then it achieved the same thing as setting to nothing using
VS.NET property window...

Thanks all for your input..
VJ

"VJ" <vijaybalki@yah oo.com> wrote in message
news:uPLg0BtyFH A.916@TK2MSFTNG P10.phx.gbl...[color=blue]
>
> I have a property for a control ( source code not available) . The
> property accepts single char as value.. so I can set it to '/' or ':' or
> anything like that...At initialize of my From I want this property to be
> set to a empty literal. I am able to do this at design time using VS.NET
> property box. This works for controls created at design time, but for some
> controls I create at run-time I want to do the same at Form_load..
>
> VJ
>
>
>[/color]

**Kevin Spencer** · Nov 17 '05, 10:45 AM

Re: Empty Character Literal

Well, Daniel, you made me do my homework. In fact, we were both wrong. The
truth is a bit more complex. It depends on the implementation used. If C# or
C++ is used, it is indeed an array of WCHAR. If C is used, it is a
null-terminated string.

Now for some aspirin...

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
Ambiguity has a certain quality to it.

"Daniel Jin" <shinakuma8@yah oo.com> wrote in message
news:1128691275 .053386.73830@g 43g2000cwa.goog legroups.com...[color=blue]
> that is not true.
>
> .net strings are not null terminated. the reason why you can have an
> empty string is because it's perfectly legal to have a 0-length array.
>
> Kevin Spencer wrote:[color=green]
>> Just a technical note about this: The reason that you can have empty
>> strings
>> is that a string is an array of char with a null terminator. That is, a
>> string is actually (in memory) one char longer than the actual string,
>> including the null terminator. A char, on the other hand, is not an
>> array,
>> but a single char.
>>
>> --
>> HTH,
>>
>> Kevin Spencer
>> Microsoft MVP
>> .Net Developer
>> Ambiguity has a certain quality to it.
>>
>> "Paul E Collins" <find_my_real_a ddress@CL4.org> wrote in message
>> news:di4djo$r06 $1@nwrdmz02.dmz .ncs.ea.ibs-infra.bt.com...[color=darkred]
>> > There is no "empty character literal", because every possible value for
>> > a
>> > char type is one character long. You can have zero length strings ("")
>> > but
>> > not zero-length characters, e.g. this will not compile:
>> >
>> > char ch = ''; // doesn't work
>> >
>> > The closest you can get is a space (' ') or a null character ('\0',
>> > ASCII
>> > zero).
>> >
>> > P.
>> >
>> >[/color][/color]
>[/color]

**Daniel Jin** · Nov 17 '05, 10:45 AM

Re: Empty Character Literal

I'm not sure what you mean by "depends on implemenation". according to Jon
Skeet's article on .NET string though, it is indeed null terminated
internally for p/invoke. so I was wrong, which makes my original point a
little inconsequential , that you don't need null termination for empty
strings, a 0-length array should do just fine.

"Kevin Spencer" wrote:
[color=blue]
> Well, Daniel, you made me do my homework. In fact, we were both wrong. The
> truth is a bit more complex. It depends on the implementation used. If C# or
> C++ is used, it is indeed an array of WCHAR. If C is used, it is a
> null-terminated string.
>
> Now for some aspirin...
>
> --
> HTH,
>
> Kevin Spencer
> Microsoft MVP
> ..Net Developer
> Ambiguity has a certain quality to it.
>
> "Daniel Jin" <shinakuma8@yah oo.com> wrote in message
> news:1128691275 .053386.73830@g 43g2000cwa.goog legroups.com...[color=green]
> > that is not true.
> >
> > .net strings are not null terminated. the reason why you can have an
> > empty string is because it's perfectly legal to have a 0-length array.
> >
> > Kevin Spencer wrote:[color=darkred]
> >> Just a technical note about this: The reason that you can have empty
> >> strings
> >> is that a string is an array of char with a null terminator. That is, a
> >> string is actually (in memory) one char longer than the actual string,
> >> including the null terminator. A char, on the other hand, is not an
> >> array,
> >> but a single char.
> >>
> >> --
> >> HTH,
> >>
> >> Kevin Spencer
> >> Microsoft MVP
> >> .Net Developer
> >> Ambiguity has a certain quality to it.
> >>
> >> "Paul E Collins" <find_my_real_a ddress@CL4.org> wrote in message
> >> news:di4djo$r06 $1@nwrdmz02.dmz .ncs.ea.ibs-infra.bt.com...
> >> > There is no "empty character literal", because every possible value for
> >> > a
> >> > char type is one character long. You can have zero length strings ("")
> >> > but
> >> > not zero-length characters, e.g. this will not compile:
> >> >
> >> > char ch = ''; // doesn't work
> >> >
> >> > The closest you can get is a space (' ') or a null character ('\0',
> >> > ASCII
> >> > zero).
> >> >
> >> > P.
> >> >
> >> >[/color]
> >[/color]
>
>
>[/color]

**Bruce Wood** · Nov 17 '05, 10:45 AM

Re: Empty Character Literal

By the way, just for your information C# 2.0 has the concept of
nullable types. There is still no such thing as the "empty character",
but in C# 2.0 you can say:

char? emptyChar = null;

which isn't quite what you were after, but I thought I'd mention it
because it's sort of related. :)

Empty Character Literal

Empty Character Literal

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