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
38  1394 
On Sat, 12 Apr 2008 15:18:22 -0700, MBSoftware <mb********@ali ce.itwrote:
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
It's shorthand for "Nullable<Point >". Value type variables (e.g. structs
like Point) cannot normally be set to null. However, you can use a
"nullable" version to allow that.
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. :)
But sometimes it makes sense to be able to treat a value type as
nullable. In that case, using the nullable version is just the ticket.
See: http://msdn2.microsoft.com/en-us/library/1t3y8s4s.aspx http://msdn2.microsoft.com/en-us/library/2cf62fcy.aspx
Also, a handy operator for resolving null-valued nullable types (e.g. to
provide a default value): http://msdn2.microsoft.com/en-us/library/ms173224.aspx
Pete
MBSoftware wrote:
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
Point is a structure and therefore a value type. Value types can not be
null. By adding ? to the declaration you make the type nullable. this is
usually used for values with a counterpart in a database which could be
null.
Personally i think it's not smart to delete code that you don't understand.
alain
On Sat, 12 Apr 2008 15:44:52 -0700, Alain Boss <ma******@hotma il.com>
wrote:
[...]
Personally i think it's not smart to delete code that you don't
understand.
Why not?
I mean, you wouldn't want to just delete it and move on. But as part of
trying to understand what the code is doing (which is what the OP was
doing), making changes to the code to see what happens, including deleting
portions of it to see what breaks, can be a very useful part of the
exploration process.
Seems like a very smart thing to do, quite the contrary to your own
thought on the matter.
Didn't you ever take things apart when you were a kid to try to figure out
how they worked?
Pete
Peter Duniho wrote:
On Sat, 12 Apr 2008 15:44:52 -0700, Alain Boss <ma******@hotma il.com>
>Personally i think it's not smart to delete code that you don't
understand.
Why not?
I mean, you wouldn't want to just delete it and move on. But as part of
trying to understand what the code is doing (which is what the OP was
doing), making changes to the code to see what happens, including
deleting portions of it to see what breaks, can be a very useful part of
the exploration process.
If there are close to perfect unit tests it may be OK.
If not then there is the risk of removing some code that was
needed and will cause problems in production.
Removing stuff that causes compile errors is best case not worst case.
Arne
Peter Duniho wrote:
On Sat, 12 Apr 2008 17:43:08 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:
>If there are close to perfect unit tests it may be OK.
If not then there is the risk of removing some code that was
needed and will cause problems in production.
What makes you think the code is production code in the first place?
How could changing non-production code "cause problems in production"?
>Removing stuff that causes compile errors is best case not worst case.
For any of what you wrote to be relevant, you are making a number of
broad assumptions that you are entirely unjustified in making.
There is absolutely nothing in the original post that justifies saying
that the person who wrote that post or what he did is "not smart".
Neither you nor Alain have nearly enough information about the situation
to pass judgment like that.
The original poster did not say whether it was production code or not.
And then it makes sense to take the conservative approach and
assume that it is production code, because the damage of giving
"production code" advice to "just for fun code" is insignificant
to giving "just for fun code" advice to "production code".
Get off your high horses. The guy's just asking a question, trying to
learn how the language works. There's no reason for you to make a
federal case out of it.
He asked a question. Alan made a good point. You made a problem
out of it.
Arne
On Sat, 12 Apr 2008 18:48:53 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:
The original poster did not say whether it was production code or not.
That's right, he didn't.
And then it makes sense to take the conservative approach and
assume that it is production code,
No, it doesn't make sense to "assume that it is production code".
If someone wanted to raise that as a possibility, and then provide a
caveat based on and qualified to that possibility, that would be one thing.
But to _assume_ that the OP is doing something stupid is, well...stupid.
As well as insulting to the OP.
Pete
On Sat, 12 Apr 2008 18:03:06 -0700, Jon Skeet [C# MVP] <sk***@pobox.co m>
wrote:
>You'll find that it can be a little inconvenient, due to the fact that
to Â*
get back to a regular value type you have to explicitly cast from the Â*
nullable version to the regular version [...]
I don't think I'd want it to behave in any other way - I certainly
wouldn't want an *implicit* conversion to a non-nullable point.
Nor I. I don't think what I wrote implied that I did, but if so, consider
this a clarification that it's not what I meant to say.
Not everything that's inconvenient is necessary bad.
Pete
On Sat, 12 Apr 2008 20:18:52 -0700, Peter Duniho
<Np*********@nn owslpianmk.comw rote:
[..]
Not everything that's inconvenient is necessary bad.
Or even "necessaril y". :)
Peter Duniho wrote:
On Sat, 12 Apr 2008 18:48:53 -0700, Arne Vajhøj <ar**@vajhoej.d kwrote:
>The original poster did not say whether it was production code or not.
That's right, he didn't.
>And then it makes sense to take the conservative approach and
assume that it is production code,
No, it doesn't make sense to "assume that it is production code".
Since you did not comment on the argument given:
# because the damage of giving
#"production code" advice to "just for fun code" is insignificant
#to giving "just for fun code" advice to "production code".
then I assume that you do not understand the argument.
Do you want me to it explain it in more detail ?
If someone wanted to raise that as a possibility, and then provide a
caveat based on and qualified to that possibility, that would be one thing.
But to _assume_ that the OP is doing something stupid is,
well...stupid. As well as insulting to the OP.
If the original poster plan on a career in software development,
then he better be prepared for that type of comments. There are
no room for "it is probably OK and let us not ask because someone
may feel offended" in software development.
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