So how well do you think you know C#?
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Smart? Nah, I give experience credit for this. Also, if you think about it, it has to be this way. Numbers aren't that different from objects in OOP. I think this code makes it more apparent:
(boolval ? new Car() : new AirPlane()).Fly();Since C# is statically typed, method selection can't be left to runtime binding. :)In this case to be able to compile it you'll have to manually cast both objects to a base class, that has a Fly() methods :) While in the example of "? 0 : 0.0" the compiler does implicit casting
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Without compiling the following code, what will be the result, if run?
class Program
{
static void Main(string[] args)
{
object r = Foo(true);
Console.WriteLine(r.GetType());
Console.ReadLine();
}static object Foo(bool e)
{
return e ? 0 : 0.0;
}
}Now compile and run the code? Are you surprised? If so, try figure it out, if not, then kudos to you :)
xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008) -
Without compiling the following code, what will be the result, if run?
class Program
{
static void Main(string[] args)
{
object r = Foo(true);
Console.WriteLine(r.GetType());
Console.ReadLine();
}static object Foo(bool e)
{
return e ? 0 : 0.0;
}
}Now compile and run the code? Are you surprised? If so, try figure it out, if not, then kudos to you :)
xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)D'ohh! My answer was: "System.Int32". (At least I'm being honest!) Although I haven't tested it, in retrospect it makes sense that the two conditional values should be the same type. Good quiz leppie!
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Yeah, makes sense to me, the ternary operator isn't allowed to return different types, so the int is implicitly cast to double, just as expected. Of course I had to add
System.to theConsolemethods to get it to compile...Yeah this has caught me a few times, usually with a compile-time error. Kind of annoying.
“Time and space can be a bitch.” –Gushie, Quantum Leap {o,o}.oO( Looking for a great RSS reader? Try FeedBeast! ) |)””’) Built with home-grown CodeProject components! -”-”-
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Without compiling the following code, what will be the result, if run?
class Program
{
static void Main(string[] args)
{
object r = Foo(true);
Console.WriteLine(r.GetType());
Console.ReadLine();
}static object Foo(bool e)
{
return e ? 0 : 0.0;
}
}Now compile and run the code? Are you surprised? If so, try figure it out, if not, then kudos to you :)
xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)leppie wrote:
compile and run the code
My computer leapt off the table, ran in circles, peed on the carpet, then spent the rest of the day sulking behind the couch, presumably calling Dial-a-Byte on my cellphone over and over again.
"A Journey of a Thousand Rest Stops Begins with a Single Movement"
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Without compiling the following code, what will be the result, if run?
class Program
{
static void Main(string[] args)
{
object r = Foo(true);
Console.WriteLine(r.GetType());
Console.ReadLine();
}static object Foo(bool e)
{
return e ? 0 : 0.0;
}
}Now compile and run the code? Are you surprised? If so, try figure it out, if not, then kudos to you :)
xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)The compiler's said test.cs(6,5): error CS0103: The name 'Console' does not exist in the current context test.cs(7,5): error CS0103: The name 'Console' does not exist in the current context because you aren't import System namespace or use full name like 'System.Console'
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Without compiling the following code, what will be the result, if run?
class Program
{
static void Main(string[] args)
{
object r = Foo(true);
Console.WriteLine(r.GetType());
Console.ReadLine();
}static object Foo(bool e)
{
return e ? 0 : 0.0;
}
}Now compile and run the code? Are you surprised? If so, try figure it out, if not, then kudos to you :)
xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)The Foo method is expecting a reference type (object), but it is getting a value type, probably double. Now the question is, does C# convert the value type to a reference type (boxing)? The reference type would be converted to a Nullable (double?), I don't think so. I don't think it will return a compile error. So I believe it will result in a runtime error (don't know what it would be). I'll run it after this post and see. Tony
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The Foo method is expecting a reference type (object), but it is getting a value type, probably double. Now the question is, does C# convert the value type to a reference type (boxing)? The reference type would be converted to a Nullable (double?), I don't think so. I don't think it will return a compile error. So I believe it will result in a runtime error (don't know what it would be). I'll run it after this post and see. Tony
Interesting, the base type of the Double is a System.ValueType, and it's base type is System.Object. Yes, I am surprised. Thanks for the puzzle.
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Double I would imagine due to this:
return e ? 0 : 0.0;. The thing with this if-expression, is that the true and false types must be of same or assignable types. In this case an int can be cast into a double, but not vice versa. Because of this, the compiler will promote the 0 to a 0.0, hence double.Hi, I ran this code and irrespective of what the parameter to foo() is, the output is system.Double
Jörgen Sigvardsson wrote:
The thing with this if-expression, is that the true and false types must be of same or assignable types. In this case an int can be cast into a double, but not vice versa. Because of this, the compiler will promote the 0 to a 0.0, hence double.
I din't get this, could you explain this please? Regards, Blumen
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Hi, I ran this code and irrespective of what the parameter to foo() is, the output is system.Double
Jörgen Sigvardsson wrote:
The thing with this if-expression, is that the true and false types must be of same or assignable types. In this case an int can be cast into a double, but not vice versa. Because of this, the compiler will promote the 0 to a 0.0, hence double.
I din't get this, could you explain this please? Regards, Blumen
If we remodel the if-expression as a function, it could be written like this:
T if-expr(bool, T trueExpression, T falseExpression).Tis an implicit type generic parameter of sorts. The compiler will at compile time determine what it is.Twill not be determined based on what is receiving it. When the compiler seesint var = boolExpr ? trueExpr : falseExpr, it will not try to deduce thatTis an int. The compiler will however examine the types oftrueExpressionandfalseExpression. In the original post, we hadintanddouble. Because we said earlier thattrueExpressionandfalseExpressionmust be of same typeT, the compiler must choose between the two types without losing information. Anintcan "fit inside" adouble, but adoublecan't fit inside anint. Thus the compiler selectsTas beingdouble. SinceTwas chosen to bedouble, the return type of the entire expression becomesT.-- Kein Mitleid Für Die Mehrheit
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If we remodel the if-expression as a function, it could be written like this:
T if-expr(bool, T trueExpression, T falseExpression).Tis an implicit type generic parameter of sorts. The compiler will at compile time determine what it is.Twill not be determined based on what is receiving it. When the compiler seesint var = boolExpr ? trueExpr : falseExpr, it will not try to deduce thatTis an int. The compiler will however examine the types oftrueExpressionandfalseExpression. In the original post, we hadintanddouble. Because we said earlier thattrueExpressionandfalseExpressionmust be of same typeT, the compiler must choose between the two types without losing information. Anintcan "fit inside" adouble, but adoublecan't fit inside anint. Thus the compiler selectsTas beingdouble. SinceTwas chosen to bedouble, the return type of the entire expression becomesT.-- Kein Mitleid Für Die Mehrheit
Jörgen Sigvardsson wrote:
If we remodel the if-expression as a function, it could be written like this: T if-expr(bool, T trueExpression, T falseExpression). T is an implicit type generic parameter of sorts. The compiler will at compile time determine what it is.
I din't understand this because I'm not good with Generics yet. But I understood that if types to be compared are different, compiler makes a choice such that there is no loss of data, I hope I'm correct here. Vielen Dank :)
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Jörgen Sigvardsson wrote:
If we remodel the if-expression as a function, it could be written like this: T if-expr(bool, T trueExpression, T falseExpression). T is an implicit type generic parameter of sorts. The compiler will at compile time determine what it is.
I din't understand this because I'm not good with Generics yet. But I understood that if types to be compared are different, compiler makes a choice such that there is no loss of data, I hope I'm correct here. Vielen Dank :)
Exactly. A common denominator. :)
Blumen wrote:
Vielen Dank
Bitteschön :)
-- Kein Mitleid Für Die Mehrheit
-
Without compiling the following code, what will be the result, if run?
class Program
{
static void Main(string[] args)
{
object r = Foo(true);
Console.WriteLine(r.GetType());
Console.ReadLine();
}static object Foo(bool e)
{
return e ? 0 : 0.0;
}
}Now compile and run the code? Are you surprised? If so, try figure it out, if not, then kudos to you :)
xacc.ide - now with TabsToSpaces support
IronScheme - 1.0 alpha 4a out now (29 May 2008)class Program
{
static void Main(string[] args)
{
object r = Foo(true); //also check for Foo(false);
Console.WriteLine(r.GetType());
Console.ReadLine();
}
static object Foo(bool e)
{
return e ? (object)0 : (object)0.0;
}
}