Ref for variables not parameters in functions?

The feature you want is called "ref locals" and it is not supported in C The CLR does support generating code that contains ref locals, and a few years ago I wrote an experimental version of C# that had the feature you want, just to see if it would work. You could do something like: Person a = whatever; ref Person be = ref a and then as you say, changes to "b" would change the contents of "a". The two variables become aliases for the same storage location Though it was a nice little feature and worked well, we decided to not take it for C#.

It's possible that it could still happen in a hypothetical future version of the language, but I would not get all excited about it in expectation; it will probably not happen (Remember, all of Eric's musings about hypothetical future versions of any Microsoft product are For Entertainment Purposes Only. ).

The feature you want is called "ref locals" and it is not supported in C#. The CLR does support generating code that contains ref locals, and a few years ago I wrote an experimental version of C# that had the feature you want, just to see if it would work. You could do something like: Person a = whatever; ref Person be = ref a; and then as you say, changes to "b" would change the contents of "a".

The two variables become aliases for the same storage location. Though it was a nice little feature and worked well, we decided to not take it for C#. It's possible that it could still happen in a hypothetical future version of the language, but I would not get all excited about it in expectation; it will probably not happen.(Remember, all of Eric's musings about hypothetical future versions of any Microsoft product are For Entertainment Purposes Only.).

I can't think of any at the moment except if we want to confuse readers... – configurator Mar 26 at 21:49 @configurator: Some algorithms become easier to write if you can make an alias to a variable and change which variable it refers to. And there are also scenarios where you can increase the speed of certain performance-sensitive code. – Eric Lippert Mar 26 at 23:41.

No it isn't possible in safe code(beyond ref function parameters). In unsafe code you might be able to use pointers to achieve that, but I don't think that's a good idea. A contains the reference to "Tom" as a value.

You'd need a reference to A to change where it points. If we consider similar code in a language which explicitly uses pointers instead of implicitly treating instances of classes as references: Person* A=new Person("Tom"); Person* B=A; B=new Person("Harry");//Changes only B Person** C=&A; (*C)=new Person("John");//Now A changes So you need a pointer to a pointer in order to change A. If you transfer this to C# you'd need a reference to a local variable.

And those are only available in the form of ref function parameters. This avoids some lifetime issues since a reference to a local variable can't safely outlive that local variable. If these are not private variables you could make B a property that modifies A in the setter.

Person B{get{return A;} set{A=value;}}.

Just as a note: C# DOES support pointers VERY similar to your sample. They are just not widely used (as I wrote in my answer). – Foxfire Feb 7 at 10:19 Yes C# it does support pointers in some limited contexts.

But it doesn't use an explicit notation for references/pointers in this context. If you declare Person as a class variables of its type are implicitly treated as a pointer/reference. – CodeInChaos Feb 7 at 10:23.

There is no direct way to do that. You can either take a source-code approach like: A = B = new Person("Harry") Or use a generic type. Something like: var A = new ReferenceHolder (new Person("Tom")); var B = A; In C# you could also use a pointer (so basically a ref type) but that approach is not statically verifyable and not suggested.

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