Someone can explain me the meanings of the ? operator applied to
declarations like that i found...
private Point? startPoint;
if i delete the ? the compiler gives me some errors but i don't understand
what's the use of ? in that declaration position...
help me please
Jun 27 '08
38  1395 
Peter Duniho wrote:
On behalf of the newsgroup generally,
Oh - you are official spokesperson for the newsgroup ...
I'm sorry that others disagree and
felt it necessary to criticize you for what is a perfectly normal and
reasonable approach to learning.
As far as I can tell then you are the only one in this thread that
has been criticizing anyone ...
Arne
"Someone can explain me the meanings of the ? operator applied to
declarations like that i found... " ... snip ...
Hi,
Nullable types on MSDN : http://msdn2.microsoft.com/en-us/library/1t3y8s4s.aspx
This article was valuable to me when I was transitioning to .Net 2.0 : (but
much more valuable was reading up on the operators it mentioned in the
latest version of Liberty's "Programmin g C#" and, of course, on MSDN) : http://www.codeproject.com/KB/cs/C__...ed_things.aspx
Note it describes ?? http://msdn2.microsoft.com/en-us/lib...8VS.80%29.aspx
as well as ? Most of the usages it mentions are NOT new to .NET 2.0,
however, but, imho, are less well known.
How delightful that we have ? as the ternary operator (in-line if/then/else
short-hand), and now for nullable types, and ?? for selecting a non-null
value from two nullable operands.
I look forward to the inevitable coming of : ??? ! :)
best, Bill
"Never stop learning, never stop testing, never stop questioning."
Peter Duniho schrieb:
You might consider therapy to help yourself with that. In the meantime,
you're just going to have to deal with being told to stop bullying
others and being bewildered as to why you've been told.
Peter, what's your problem? You're the only bully in this thread. Just
read your posts again. Then count to four and close this thread.
Thank you!
Bill Woodruff wrote:
"Someone can explain me the meanings of the ? operator applied to
declarations like that i found... " ... snip ...
Hi,
Nullable types on MSDN :
http://msdn2.microsoft.com/en-us/library/1t3y8s4s.aspx
This article was valuable to me when I was transitioning to .Net 2.0
: (but much more valuable was reading up on the operators it
mentioned in the latest version of Liberty's "Programmin g C#" and, of
course, on MSDN) :
http://www.codeproject.com/KB/cs/C__...ed_things.aspx
Note it describes ??
http://msdn2.microsoft.com/en-us/lib...8VS.80%29.aspx
as well as ? Most of the usages it mentions are NOT new to .NET 2.0,
however, but, imho, are less well known.
How delightful that we have ? as the ternary operator (in-line
if/then/else short-hand), and now for nullable types, and ?? for
selecting a non-null value from two nullable operands.
I look forward to the inevitable coming of : ??? ! :)
Would that be:
x = a ??? b!;
or
x = ???! b;
or
x ?= ?? b!;
?
>
best, Bill
"Never stop learning, never stop testing, never stop questioning."
Ben Voigt [C++ MVP] wrote:
Bill Woodruff wrote:
>"Someone can explain me the meanings of the ? operator applied to
declarations like that i found... " ... snip ...
Hi,
Nullable types on MSDN :
http://msdn2.microsoft.com/en-us/library/1t3y8s4s.aspx
This article was valuable to me when I was transitioning to .Net 2.0
: (but much more valuable was reading up on the operators it
mentioned in the latest version of Liberty's "Programmin g C#" and, of
course, on MSDN) :
http://www.codeproject.com/KB/cs/C__...ed_things.aspx
Note it describes ??
http://msdn2.microsoft.com/en-us/lib...8VS.80%29.aspx
as well as ? Most of the usages it mentions are NOT new to .NET 2.0,
however, but, imho, are less well known.
How delightful that we have ? as the ternary operator (in-line
if/then/else short-hand), and now for nullable types, and ?? for
selecting a non-null value from two nullable operands.
I look forward to the inevitable coming of : ??? ! :)
Would that be:
x = a ??? b!;
or
x = ???! b;
or
x ?= ?? b!;
?
>best, Bill
"Never stop learning, never stop testing, never stop questioning."
How about ??? for, and I don't know the term for this although I believe
it has one, reading objects from properties/fields on objects, and then
reading yet another propert/field on that object, etc., but stop on the
first null-reference.
For instance:
TreeNode node = = node ??? Parent ??? Parent ??? Parent;
to get the grand-grandparent of the node, if available.
Basically the above code (and I've seen the construct, only with :
instead of ??? I think) could be translated to:
TreeNode node;
if (node != null && node.Parent != null && node.Parent.Par ent != null &&
node.Parent.Par ent.Parent != null)
node = node.Parent.Par ent.Parent;
else
node = null;
But in lieu of the previous post, personally I like this particular
construct:
(bb | !bb)?
--
Lasse Vågsæther Karlsen
mailto:la***@vk arlsen.no http://presentationmode.blogspot.com/
PGP KeyID: 0xBCDEA2E3
On Apr 14, 8:24 am, Lasse Vågsæther Karlsen <la...@vkarlsen .nowrote:
How about ??? for, and I don't know the term for this although I believe
it has one, reading objects from properties/fields on objects, and then
reading yet another propert/field on that object, etc., but stop on the
first null-reference.
I know in Groovy it's called the safe-dereference operator - but I
like their syntax for it, which is ?. so your example would be:
node?.Parent?.P arent?.Parent
Note that the type of each expression doesn't have to be the same -
because the result will be null if any of the dereferencing fails, the
overall expression type can just be the type of the full expression
with normal dereferencing, providing it's a nullable type. For
instance:
string boss = employee?.Manag er?.FullName;
where the types involved could be Employee, IManager, and string
respectively. That allows a handy conjunction with ?? as well:
string boss = employee?.Manag er?.FullName ?? "Unknown";
Jon
On Mon, 14 Apr 2008 04:15:34 -0700, Alain Boss <ma******@hotma il.com>
wrote:
Peter, what's your problem? You're the only bully in this thread.
If it's being a bully to tell a bully to stop bullying, yes. I suppose
you might be right. Otherwise, you don't have a leg to stand on.
Just read your posts again. Then count to four and close this thread.
If that's such good advice, I'm wondering why you are giving it rather
than following it.
On Apr 12, 6:38 pm, "Peter Duniho" <NpOeStPe...@nn owslpianmk.com>
wrote:
You'll find that it can be a little inconvenient, due to the fact that to
get back to a regular value type you have to explicitly cast from the
nullable version to the regular version (e.g. "Point point =
(Point)startPoi nt;"). This means without the cast, the "nullable" trait
tends to propagate through your code as you copy values from one variable
to another. :)
No need for a cast:
Point point = startPoint.Valu e;
Will work fine.. but you must test startPoint.HasV alue first.
Peter Duniho wrote:
On Mon, 14 Apr 2008 04:15:34 -0700, Alain Boss <ma******@hotma il.com>
wrote:
>Peter, what's your problem? You're the only bully in this thread.
If it's being a bully to tell a bully to stop bullying, yes. I suppose
you might be right. Otherwise, you don't have a leg to stand on.
>Just read your posts again. Then count to four and close this thread.
If that's such good advice, I'm wondering why you are giving it rather
than following it.
Well, i guess it would have been much easier for you to count to 2
rather than 4. I'm still not sure what you think it was where i bullied
anybody. It was you who called me stupid, it was you who told arne to
make a therapy. The only thing i regret is that i reply to another of
your useless posts. mea culpa!
On Mon, 14 Apr 2008 15:35:51 -0700, Alain Boss <ma******@hotma il.com>
wrote:
Well, i guess it would have been much easier for you to count to 2
rather than 4.
Not satisfied with calling the OP "not smart", you now choose to insult me
as well? No doubt you'll not understand why this most recent post of
yours was offensive as well.
I'm still not sure what you think it was where i bullied anybody.
I don't understand why you aren't sure of "what I think it was where you
bullied anybody", since the flow of messages is quite clear. The first
post to which I replied is the obvious candidate. Why else would I have
made the reply I did? The later post in which you reiterated your
assertion would be a second example.
It was you who called me stupid,
No, I didn't. The only post in which I used that word, I was referring to
Arne's assumption that the OP is working with production code.
It was the assumption itself that I was calling stupid, not the individual
making it, and you claim to not even have made that assumption anyway so
it wouldn't apply to you in any case, however you interpreted it.
it was you who told arne to make a therapy.
Only because he, like you, is incapable of recognizing when someone else
has made a valid point that hurts his pride. And only after he insisted
on engaging in his own bullying. It's hardly bullying to recommend to
someone that they seek professional help when they are in fact apparently
in need of it and demonstrate that repeatedly over a significant period of
time.
In any case, whether or not I was bullying a couple of bullies has nothing
to do with whether they are bullies in the first place.
The only thing i regret is that i reply to another of your useless
posts. mea culpa!
Yes, it's your fault.
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