dotNET Rant [modified]
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In this context the
falseis about identity, not value: it returnsfalsebecause the the two instances are distinct (different object instances).Steve
understood, just not the expected result in the context I was doing the code. The example given was way simplified.
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No, it isn't, it's correct.
obviously, my statement was an opinion. but, i'll deal with reality rather than my wishfulness.
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My edit was too slow: You could put a NaN into an ArrayList and then use Contains, only to find that the NaN has "disappeared" but is still taking up a slot somewhere and you can clearly see it in the debugger.. :) edit: more generally, doing things like that break the Liskov substitution principle - that is Bad. edit2: It's almost 2am so I'm going to sleep for a bit.. I'll definitely check this thread out tomorrow morning though
modified on Thursday, May 6, 2010 7:51 PM
harold aptroot wrote:
doing things like that
not sure what you mean. The arrayList.Contains "failing" or my argument that == and Equals should be the same?
harold aptroot wrote:
iskov substitution principle
Don't know what that is I'll have to look it up.
harold aptroot wrote:
almost 2am
go get some sleep. and dream beautiful dreams.
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ahmed zahmed wrote:
whether I use == or .Equals should be semantically the same.
But it is not. Consider this:
string s = "ahmed";
string s1 = "zahmed";Console.WriteLine(s.Equals(s1.Substring(1)));
Console.WriteLine(s == (s1.Substring(1)));Console.WriteLine((object)s == (s1.Substring(1)));
What do you think the output will be? It has to be: 1. true 2. true (the operator == in string is overloaded) 3. false (reference comparison)
To complicate matters: you do know some of those strings will be interned, and some won't. Now this thread is more technical than any of today's threads in the C# forum. It is time you realize this still is The Lounge. :)
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ok, this is not a programming question. It's a rant! given,
object one = 0;
object two = 0;
bool same = one == two;what would you expect the value of
sameto be? WRONG! it's false! Whoever thought that was a valid result, is cracked!:mad::mad::mad::mad::mad: [edit] so, after going home and resting my brain a bit. it seems as though i'm the one that was cracked. thanks for the refresher course everyone. it is of course doing a reference comparison. which is correct. you all know how it is when you struggle with something and get too close to the trees to see the forest. anyway thanks to everyone for being your normally brutally honest selves. cheers. :-D [/edit]Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/modified on Friday, May 7, 2010 1:08 AM
You have to remember, they were copying Java. You need to use object.Equals for that situation. It's not intuitive, but it's the choice the designers made.
I can imagine the sinking feeling one would have after ordering my book, only to find a laughably ridiculous theory with demented logic once the book arrives - Mark McCutcheon
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Is has to be like that, though. Otherwise either the "a.Equals(a) must be true" identity is violated (which would make some of the non-generic .NET 1.1 collections fail*), or the rules for IEEE floating point comparison are.. * you could put a NaN into an ArrayList and then use Contains, only to find that the NaN has "disappeared" but is still taking up a slot somewhere and you can clearly see it in the debugger.. :)
modified on Thursday, May 6, 2010 7:35 PM
Ian's next book could be titled "The Mystery of the Vanishing NaN" then? :)
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The context is comparing DbParameter's (parameters to a PreparedCommand) to know whether the result is cached or not. So it's not as simple as it may seem. In any case, seems to me that since only primitives get boxed, then that condition should be checked in the object.Equals code. Thanks for the suggestion.
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http://obamacaretruth.org/ahmed zahmed wrote:
since only primitives get boxed
only value types get boxed, i.e. when an object is required. I wouldn't call a struct primitive. :)
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To complicate matters: you do know some of those strings will be interned, and some won't. Now this thread is more technical than any of today's threads in the C# forum. It is time you realize this still is The Lounge. :)
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Yes that's why I did not do: :)
string s = "ahmed";
String s1 = "ahmed"; -
ok, this is not a programming question. It's a rant! given,
object one = 0;
object two = 0;
bool same = one == two;what would you expect the value of
sameto be? WRONG! it's false! Whoever thought that was a valid result, is cracked!:mad::mad::mad::mad::mad: [edit] so, after going home and resting my brain a bit. it seems as though i'm the one that was cracked. thanks for the refresher course everyone. it is of course doing a reference comparison. which is correct. you all know how it is when you struggle with something and get too close to the trees to see the forest. anyway thanks to everyone for being your normally brutally honest selves. cheers. :-D [/edit]Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/modified on Friday, May 7, 2010 1:08 AM
I would expect it to be false. You are comparing two object instances for reference equality, and clearly
oneis not in the same memory location astwo.Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
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Rama Krishna Vavilala wrote:
It has to be false. What else can it be?
Why? One would expect that the comparators of the boxed values would be used. so, the result would be true, as I initially expected. I understand what's happening, but I don't understand why the dotNETtors decided this was correct.
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http://obamacaretruth.org/ahmed zahmed wrote:
One would expect that the comparators of the boxed values would be used. so, the result would be true, as I initially expected.
Why do you think these are being boxed? You are clearly assigning values to an object instance. This doesn't result in any boxing operations.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
-
ok, this is not a programming question. It's a rant! given,
object one = 0;
object two = 0;
bool same = one == two;what would you expect the value of
sameto be? WRONG! it's false! Whoever thought that was a valid result, is cracked!:mad::mad::mad::mad::mad: [edit] so, after going home and resting my brain a bit. it seems as though i'm the one that was cracked. thanks for the refresher course everyone. it is of course doing a reference comparison. which is correct. you all know how it is when you struggle with something and get too close to the trees to see the forest. anyway thanks to everyone for being your normally brutally honest selves. cheers. :-D [/edit]Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/modified on Friday, May 7, 2010 1:08 AM
Of course it's false! You just compared the references of two OBJECTS, not two values. It seems that you're the one who's "cracked".
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009... -
Ian's next book could be titled "The Mystery of the Vanishing NaN" then? :)
Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles]
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We all depend on the beast below.
Luc Pattyn wrote:
The Mystery of the Vanishing NaN
It's no mystery that any NaaN placed in front of me will vanish.
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ok, this is not a programming question. It's a rant! given,
object one = 0;
object two = 0;
bool same = one == two;what would you expect the value of
sameto be? WRONG! it's false! Whoever thought that was a valid result, is cracked!:mad::mad::mad::mad::mad: [edit] so, after going home and resting my brain a bit. it seems as though i'm the one that was cracked. thanks for the refresher course everyone. it is of course doing a reference comparison. which is correct. you all know how it is when you struggle with something and get too close to the trees to see the forest. anyway thanks to everyone for being your normally brutally honest selves. cheers. :-D [/edit]Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/modified on Friday, May 7, 2010 1:08 AM
ahmed zahmed wrote:
Whoever thought that was a valid result, is cracked
Well duh, it's supposed to be different, you're one who's cracked! Why don't you read up on value vs. reference comparisons. Marc
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obviously, my statement was an opinion. but, i'll deal with reality rather than my wishfulness.
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/ahmed zahmed wrote:
my statement was an opinion
No, your statement is not an opinion, it is a falsehood. Much like the return of your two object comparison, hahaha. Marc
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ahmed zahmed wrote:
my statement was an opinion
No, your statement is not an opinion, it is a falsehood. Much like the return of your two object comparison, hahaha. Marc
nice. hope you feel good about yourself.
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/ -
ahmed zahmed wrote:
since only primitives get boxed
only value types get boxed, i.e. when an object is required. I wouldn't call a struct primitive. :)
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yes, true enough. still in the context where i'm dealing with these boxed "value types" the only values boxed will be primitives. but thanks for the reminder.
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/ -
I would expect it to be false. You are comparing two object instances for reference equality, and clearly
oneis not in the same memory location astwo.Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
yes, a distinction i forgot in my frustration. thanks for the refresher.
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/ -
Of course it's false! You just compared the references of two OBJECTS, not two values. It seems that you're the one who's "cracked".
A guide to posting questions on CodeProject[^]
Dave Kreskowiak Microsoft MVP Visual Developer - Visual Basic
2006, 2007, 2008
But no longer in 2009...well, you know how it is, i'm sure when you're doing something all day long and your brain gets fried. yep, i was the one cracked, for sure.
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/ -
ahmed zahmed wrote:
Whoever thought that was a valid result, is cracked
Well duh, it's supposed to be different, you're one who's cracked! Why don't you read up on value vs. reference comparisons. Marc
lol, yep you are right. that's me, the cracked one.
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/ -
ahmed zahmed wrote:
One would expect that the comparators of the boxed values would be used. so, the result would be true, as I initially expected.
Why do you think these are being boxed? You are clearly assigning values to an object instance. This doesn't result in any boxing operations.
Scott Dorman
Microsoft® MVP - Visual C# | MCPD President - Tampa Bay IASA [Blog][Articles][Forum Guidelines]
Hey, hey, hey. Don't be mean. We don't have to be mean because, remember, no matter where you go, there you are. - Buckaroo Banzai
ok, perhaps I'm misunderstanding something, but aren't value types boxed when assigned to an object? or passed as a parameter to a function whose parameter type is object?
Fight Big Government:
http://obamacareclassaction.com/
http://obamacaretruth.org/