Fave Operator of the Day
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For the really nerdy:
string value = value1 ?? value2 ?? value3 ?? finalDefaultValue;Deja View - the feeling that you've seen this post before.
OK. For us poor, ignorant C++ jocks, please explain what that abomination does. I'm guessing it's something like this:
if (value1 != NULL) value = value1;
else if (value2 != NULL) value = value2;
else if (value3 != NULL) value = value3;
else value = finalDefaultValue;
Software Zen:
delete this; -
OK. For us poor, ignorant C++ jocks, please explain what that abomination does. I'm guessing it's something like this:
if (value1 != NULL) value = value1;
else if (value2 != NULL) value = value2;
else if (value3 != NULL) value = value3;
else value = finalDefaultValue;
Software Zen:
delete this;Yup - that's exactly what it does - it coalesces through the chain until it finds a none-null value.
Deja View - the feeling that you've seen this post before.
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Yup - that's exactly what it does - it coalesces through the chain until it finds a none-null value.
Deja View - the feeling that you've seen this post before.
I'm curious. Does this pattern occur often enough in .NET programming that it was worth adding an operator for it? Or is it the case that, since the operator is available, you use that pattern more often?
Software Zen:
delete this; -
I'm curious. Does this pattern occur often enough in .NET programming that it was worth adding an operator for it? Or is it the case that, since the operator is available, you use that pattern more often?
Software Zen:
delete this;I use ?? from time to time, but I needed more than a single ?? in an expression. I think a "?." operator would be much more useful than ??. "obj?.Method()" could be syntax sugar for "(obj != null) ? obj.Method() : null" (except that "obj" is evaluated only once). Hopefully MS will add something like that to C# 4.0...
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I'm curious. Does this pattern occur often enough in .NET programming that it was worth adding an operator for it? Or is it the case that, since the operator is available, you use that pattern more often?
Software Zen:
delete this;Gary Wheeler wrote:
Does this pattern occur often enough in .NET
In normal code, there is often times you want to get a value back, even if it is a specific default value rather than having to deal with nulls. Now that there is nullable types, it happens quite a bit more. While I am not sure that there is a need for a chain of values as mentioned in the prior post, the ?? is handy to have around.
Rocky <>< Blog Post: LINQ Scores a Yahtzee! Tech Blog Post: Cheap Biofuels and Synthetics coming soon?
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For the really nerdy:
string value = value1 ?? value2 ?? value3 ?? finalDefaultValue;Deja View - the feeling that you've seen this post before.
Ok, so we comparing nerdiness, beat this one for flavour :)
class Foo
{
CallTargetWithContext0 target0;
CallTargetWithContext1 target1;
CallTargetWithContext2 target2;
CallTargetWithContext3 target3;
CallTargetWithContext4 target4;
CallTargetWithContext5 target5;
CallTargetWithContextN targetN;public Foo(Delegate target)
{
target =
(target0 = target as CallTargetWithContext0) ??
(target1 = target as CallTargetWithContext1) ??
(target2 = target as CallTargetWithContext2) ??
(target3 = target as CallTargetWithContext3) ??
(target4 = target as CallTargetWithContext4) ??
(target5 = target as CallTargetWithContext5) ??
// for some reason the last one needs a cast...
((Delegate)(targetN = target as CallTargetWithContextN));
}
}xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach." -
The C# 2.0 null coalescing operator
??God bless its little cotton socks.cheers, Chris Maunder
CodeProject.com : C++ MVP
I just had to show someone how to use that yesterday. Also remember it was one of the coding questions of the day here a while back. My favorite operator is noop. I would get it on a tag if I wasn't afraid muggles would mispronounce it.
Need a C# Consultant? I'm available.
Happiness in intelligent people is the rarest thing I know. -- Ernest Hemingway -
yeah, I still from time to time type if (myobj) and then remember.
Christian Graus - Microsoft MVP - C++ "also I don't think "TranslateOneToTwoBillion OneHundredAndFortySevenMillion FourHundredAndEightyThreeThousand SixHundredAndFortySeven()" is a very good choice for a function name" - SpacixOne ( offering help to someone who really needed it ) ( spaces added for the benefit of people running at < 1280x1024 )
Discovering that C# does not support that, my happy face turned into a sad face :(
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Personally, i'd have preferred something along the lines of the GNU C "shortcut ternary" operator (which it closely resembles). But then, i'd have liked it if C# interpreted
nullvalues asfalseinstead of requiring an explicit comparison... :->----
...the wind blows over it and it is gone, and its place remembers it no more...
Frankly, I am getting tired of null reference exceptions. I just wish C#/.NET wouldn't be so finicky about null references. For example the latest issue I had was with a MediaPlayer object, where I close the (possibly) existing player before starting a new one: player.Stop(); player = new MediaPlayer(); ... But if I haven't already created a MediaPlayer I get a freaking null reference exception. Of course I know that I should know better and test player for null, but my point is I don't CARE if player.Stop() fails, it's not going to aversely affect my function at all anyway, and my argument is that I bet in 80-90% of cases, null reference exceptions that slip through in production code probably would work fine if they were simply ignored, like my example above. Who's with me for demanding that null reference exceptions be ignored by default and only thrown in blocks explicitly marked as such! Lol, just a mini-rant. :P
{o,o}.oO( Did somebody say “mouse”? ) |)””’) -”-”-
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Ok, so we comparing nerdiness, beat this one for flavour :)
class Foo
{
CallTargetWithContext0 target0;
CallTargetWithContext1 target1;
CallTargetWithContext2 target2;
CallTargetWithContext3 target3;
CallTargetWithContext4 target4;
CallTargetWithContext5 target5;
CallTargetWithContextN targetN;public Foo(Delegate target)
{
target =
(target0 = target as CallTargetWithContext0) ??
(target1 = target as CallTargetWithContext1) ??
(target2 = target as CallTargetWithContext2) ??
(target3 = target as CallTargetWithContext3) ??
(target4 = target as CallTargetWithContext4) ??
(target5 = target as CallTargetWithContext5) ??
// for some reason the last one needs a cast...
((Delegate)(targetN = target as CallTargetWithContextN));
}
}xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach."Oooh - I like that one. The code is completely impenetrable and adds unnecessary complexity. I like it.:-D
Deja View - the feeling that you've seen this post before.
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The C# 2.0 null coalescing operator
??God bless its little cotton socks.cheers, Chris Maunder
CodeProject.com : C++ MVP
It is up there, but not equal to the nullable int (not an assignment operator like ??, but a little known feature and useful none the less) int? myNullableInt = null; Console.WriteLine(myNullableInt ?? "Null"); myNullableInt = 1; Console.WriteLine(myNullableInt ?? "Null"); Outputs: null 1
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Jim Crafton wrote:
is there a VB equivalent
Who cares ;)
WPF - Imagineers Wanted Follow your nose using DoubleAnimationUsingPath
norm .net wrote:
Jim Crafton wrote: is there a VB equivalent Who cares
People in jobs that require the use of VB. >.<
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Oooh - I like that one. The code is completely impenetrable and adds unnecessary complexity. I like it.:-D
Deja View - the feeling that you've seen this post before.
Pete O`Hanlon wrote:
The code is completely impenetrable and adds unnecessary complexity.
In fact, the code is highly optimized for typesafe assignment. IIRC when I tried to rewrite with if's, the generated IL was a lot more 'verbose'. :)
xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach." -
Frankly, I am getting tired of null reference exceptions. I just wish C#/.NET wouldn't be so finicky about null references. For example the latest issue I had was with a MediaPlayer object, where I close the (possibly) existing player before starting a new one: player.Stop(); player = new MediaPlayer(); ... But if I haven't already created a MediaPlayer I get a freaking null reference exception. Of course I know that I should know better and test player for null, but my point is I don't CARE if player.Stop() fails, it's not going to aversely affect my function at all anyway, and my argument is that I bet in 80-90% of cases, null reference exceptions that slip through in production code probably would work fine if they were simply ignored, like my example above. Who's with me for demanding that null reference exceptions be ignored by default and only thrown in blocks explicitly marked as such! Lol, just a mini-rant. :P
{o,o}.oO( Did somebody say “mouse”? ) |)””’) -”-”-
logan1337 wrote:
and my argument is that I bet in 80-90% of cases, null reference exceptions that slip through in production code probably would work fine if they were simply ignored, like my example above.
Are you nuts? :~ You're responsible for telling the computer what to do. If you hand it a null reference, your method call can't actually be called. If you didn't need it to be called, you shouldn't have written it! Just think - you could have been trying to do anything. Essentially, you're saying that the runtime should plow through catastrophic bugs and attempt to keep executing something, on the assumption that major portions of your code aren't actually important anyway! No. No, no no. This is the road to unpredictable software, bugs that can never be reliably reproduced or tracked back to their original cause, shoddy software that works once, for the single scenario the developer tests under, but trashes the machines of half the end users. :sigh:
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...the wind blows over it and it is gone, and its place remembers it no more...
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It is up there, but not equal to the nullable int (not an assignment operator like ??, but a little known feature and useful none the less) int? myNullableInt = null; Console.WriteLine(myNullableInt ?? "Null"); myNullableInt = 1; Console.WriteLine(myNullableInt ?? "Null"); Outputs: null 1
MrEyes wrote:
Outputs: null
No that would be "Null" :)
xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach." -
MrEyes wrote:
Outputs: null
No that would be "Null" :)
xacc.ide
IronScheme a R5RS-compliant Scheme on the DLR
The rule of three: "The first time you notice something that might repeat, don't generalize it. The second time the situation occurs, develop in a similar fashion -- possibly even copy/paste -- but don't generalize yet. On the third time, look to generalize the approach." -
logan1337 wrote:
and my argument is that I bet in 80-90% of cases, null reference exceptions that slip through in production code probably would work fine if they were simply ignored, like my example above.
Are you nuts? :~ You're responsible for telling the computer what to do. If you hand it a null reference, your method call can't actually be called. If you didn't need it to be called, you shouldn't have written it! Just think - you could have been trying to do anything. Essentially, you're saying that the runtime should plow through catastrophic bugs and attempt to keep executing something, on the assumption that major portions of your code aren't actually important anyway! No. No, no no. This is the road to unpredictable software, bugs that can never be reliably reproduced or tracked back to their original cause, shoddy software that works once, for the single scenario the developer tests under, but trashes the machines of half the end users. :sigh:
----
...the wind blows over it and it is gone, and its place remembers it no more...
Hahaha, like software isn't unpredictable already! And I'm not responsible for telling the computer what to do, the computer is responsible for doing what I ultimately want it to do. There's a difference. In a perfect world, where programmers were perfect beings and never made mistakes, what you're saying would be perfectly valid. But just think about it: if the computer (that is, the developers designing the system) took into account the potential for programmers to make mistakes, or simply to FORGET things, things might be a lot different. I'm not actually proposing this, but I just wanted to get people thinking about it in a different way. We're programming systems from the perspective that programmers ARE JUST LIKE PROGRAMS--that a programmer will write a program as accurately as a computer will execute it. But this isn't the case. Computers need to be designed from an interpretive perspective, like language. The English language (or any spoken language) is full of ambiguous, imprecise statements because that's how humans think. Why should we be forced to communicate with a computer any differently? ... I just read my last sentence and realized I'm opening myself to all kinds of flaming. So I'll cool down and pull back a little. All I want is for a null reference to be like "no object" so that if I execute a method on "no object" NOTHING HAPPENS! Maybe in some kind of debug mode it would give me a warning, or even an exception, but for production code, are we really saying that the program should break just because the code isn't written perfectly? I mean, what's more important here, that the program be perfect or that the user be able to use it? In my own defense, newer technologies are actually starting to see the benefit of this. Take WPF for instance. If you databind an object to a WPF control that does not support rendering the object, or cannot interpret it (for example in a list view hosting various types of objects), the program will not bomb on you. In fact nothing will happen at all, except that you'll get a silent message on the debug output window. Sure that little part of the program might not end up working, but it doesn't prevent the user from continuing to use the program. In fact it may not even be noticable to the user, and that's a heck of a lot better than throwing up an ugly Exception dialog, announcing to the world that the software basically sucks. I'd personally like to see a shift towards these kind of "silent" failures over big ugly error dialogs.
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Hahaha, like software isn't unpredictable already! And I'm not responsible for telling the computer what to do, the computer is responsible for doing what I ultimately want it to do. There's a difference. In a perfect world, where programmers were perfect beings and never made mistakes, what you're saying would be perfectly valid. But just think about it: if the computer (that is, the developers designing the system) took into account the potential for programmers to make mistakes, or simply to FORGET things, things might be a lot different. I'm not actually proposing this, but I just wanted to get people thinking about it in a different way. We're programming systems from the perspective that programmers ARE JUST LIKE PROGRAMS--that a programmer will write a program as accurately as a computer will execute it. But this isn't the case. Computers need to be designed from an interpretive perspective, like language. The English language (or any spoken language) is full of ambiguous, imprecise statements because that's how humans think. Why should we be forced to communicate with a computer any differently? ... I just read my last sentence and realized I'm opening myself to all kinds of flaming. So I'll cool down and pull back a little. All I want is for a null reference to be like "no object" so that if I execute a method on "no object" NOTHING HAPPENS! Maybe in some kind of debug mode it would give me a warning, or even an exception, but for production code, are we really saying that the program should break just because the code isn't written perfectly? I mean, what's more important here, that the program be perfect or that the user be able to use it? In my own defense, newer technologies are actually starting to see the benefit of this. Take WPF for instance. If you databind an object to a WPF control that does not support rendering the object, or cannot interpret it (for example in a list view hosting various types of objects), the program will not bomb on you. In fact nothing will happen at all, except that you'll get a silent message on the debug output window. Sure that little part of the program might not end up working, but it doesn't prevent the user from continuing to use the program. In fact it may not even be noticable to the user, and that's a heck of a lot better than throwing up an ugly Exception dialog, announcing to the world that the software basically sucks. I'd personally like to see a shift towards these kind of "silent" failures over big ugly error dialogs.
logan1337 wrote:
And I'm not responsible for telling the computer what to do, the computer is responsible for doing what I ultimately want it to do. There's a difference.
You're thinking of a wife. And even those don't always do what you ultimately want. Computers are the beige ones that only do exactly what you tell them to.
logan1337 wrote:
In a perfect world, where programmers were perfect beings and never made mistakes, what you're saying would be perfectly valid.
No, actually, in that case it wouldn't matter because there would be no programs trying to dereference null pointers and therefore all method calls specified could be made. You might not realize this, but the null reference exception is actually a huge convenience, something that a fair amount of runtime logic is devoted to making easier for you to detect and debug.
logan1337 wrote:
The English language (or any spoken language) is full of ambiguous, imprecise statements because that's how humans think.
Wrong. About the "that's how humans think" bit. Of course there is ambiguity in our language. There's ambiguity in the statement you posted earlier as well - player is a variable, an ambiguity, a reference that won't be resolved until runtime. The difference is, humans take initiative - we expect them to work based on past experience, and so upon instructing an employee to turn off the radio and play a CD, this employee can, upon failing to find any radio in the vicinity, look back at his past dealings with you and recall that you are stone-deaf and tend to assume the presence of radios when there are none. The computer does not have this luxury. It doesn't know the difference between a media player, a missile launch controller, or a game of "decorate the cakes". We may, at some point, reach the level of ability that would let us allow and expect value judgments from our machines. But we're no where near there now. Trying to allow such things at present would put us in the frustrating position of the simpleton's master, continually dealing with the disastrous effects that result from relying on the common sense of something that has none.
logan1337 wrote:
All I want is for a null reference to be like "no object" so that if I execute a method on "no object" NOTHING HAPPENS!
Now, that's actually a
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logan1337 wrote:
And I'm not responsible for telling the computer what to do, the computer is responsible for doing what I ultimately want it to do. There's a difference.
You're thinking of a wife. And even those don't always do what you ultimately want. Computers are the beige ones that only do exactly what you tell them to.
logan1337 wrote:
In a perfect world, where programmers were perfect beings and never made mistakes, what you're saying would be perfectly valid.
No, actually, in that case it wouldn't matter because there would be no programs trying to dereference null pointers and therefore all method calls specified could be made. You might not realize this, but the null reference exception is actually a huge convenience, something that a fair amount of runtime logic is devoted to making easier for you to detect and debug.
logan1337 wrote:
The English language (or any spoken language) is full of ambiguous, imprecise statements because that's how humans think.
Wrong. About the "that's how humans think" bit. Of course there is ambiguity in our language. There's ambiguity in the statement you posted earlier as well - player is a variable, an ambiguity, a reference that won't be resolved until runtime. The difference is, humans take initiative - we expect them to work based on past experience, and so upon instructing an employee to turn off the radio and play a CD, this employee can, upon failing to find any radio in the vicinity, look back at his past dealings with you and recall that you are stone-deaf and tend to assume the presence of radios when there are none. The computer does not have this luxury. It doesn't know the difference between a media player, a missile launch controller, or a game of "decorate the cakes". We may, at some point, reach the level of ability that would let us allow and expect value judgments from our machines. But we're no where near there now. Trying to allow such things at present would put us in the frustrating position of the simpleton's master, continually dealing with the disastrous effects that result from relying on the common sense of something that has none.
logan1337 wrote:
All I want is for a null reference to be like "no object" so that if I execute a method on "no object" NOTHING HAPPENS!
Now, that's actually a
Shog9 wrote:
You might not realize this, but the null reference exception is actually a huge convenience, something that a fair amount of runtime logic is devoted to making easier for you to detect and debug.
I am aware that it is very useful to programmers, but it's not useful to users, when the program they're using stops working for reasons they don't even understand.
Shog9 wrote:
The difference is, humans take initiative - we expect them to work based on past experience, and so upon instructing an employee to turn off the radio and play a CD, this employee can, upon failing to find any radio in the vicinity, look back at his past dealings with you and recall that you are stone-deaf and tend to assume the presence of radios when there are none. The computer does not have this luxury. It doesn't know the difference between a media player, a missile launch controller, or a game of "decorate the cakes".
I tend to think of computers merely as enablers of communication. There is communication between the developer of a system and the programmers utilizing it. It is, after all the system we are using, built upon a computer, rather than the computer itself. The computer is merely an encapsulation of many many levels of abstraction layered upon one another. As such, yes the computer as a MACHINE does exactly and only what it is instructed to do (assuming it is built properly, and ignoring the potential for physical error), but a program is something much more high-level than the computer. The operating system is, after all, itself a program, that hosts client programs and abstracts away the lower-level machine.
Shog9 wrote:
Someone else in this thread proposed the addition of a new operator, ?.
I was, in fact, one of the gentlemen who brainstormed on this in another thread[^]. :)
Shog9 wrote:
both require the programmer to explicitly specify that it's ok to do nothing in null cases.
I'm not proposing otherwise. My desire is to have the behavior default to
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Jim Crafton wrote:
Is this just a C# thing or is there a VB equivalent (I'm almost afraid to ask what that monstrosity would look like)?
Monstrosity you say? In VB? Unthinkable! :rolleyes: Classic VB (and VB.NET) has a ternary operator... except, it isn't really an operator. The IIF() function takes three operands, if the first is true it returns the second, otherwise it returns the third. Unlike the C++/C# ternary operator, this will always evaluate all three expressions (being a function call rather than an operator, it has to). This provided yet another pitfall when using VB, as expressions such as:
someVar = IIF(boolVar, HorriblyDestructiveCall1(), EvenMoreDestructiveCall())...would end up trashing whatever global state you were manipulating with the two functions twice, once for each call (remember, this is VB - of course there's a horrible, fragile, global state of some sort). VB9 now provides a true ternary operator - If. So you can write:someVar = If(boolVar, HorriblyDestructiveCall1(), EvenMoreDestructiveCall())... and only one of the possible functions will be called. Or, for the null coalescing version:someVar = If(possiblyNothing, BetterThanNothing())Good times...----
...the wind blows over it and it is gone, and its place remembers it no more...
All of those examples remind me of the days I was an employee. I don't have those examples anymore. Feels good. Feels really good. In fact I'll walk out my office door and go lay on my bed for a minute and savor my daily commute it feels so good. Then I'll get some food right out of my kitchen, right next to my office. A bit of honey encrusted cured ham on some black bread with yellow mustard and sharp cheddar cheese. Yeah... I really miss being the turd-licking employee that had to ponder if (possiblyNothing, BetterThanNothing()) that had to ask about everyone's Friday plans because that's all you look forward to as an employee is Friday. All of the above was said in PureJest version 2.0 running against the Sarcasm Framework 3.5 that was just updated on my Complete Cynic OS version 711.:laugh: