unboxing

Suppose I have a simple data type like: data Cell = Open | Blocked and I'd like to use a UArray Int Cell . Is there an easy way to do this? Can I somehow reuse the definition for UArray Int Bool ? crockeea This answer explains why Vectors are better than Arrays, so I'm going to give you the answer for unboxed vectors. I did try deriving an MArray and IArray instance for Cell based on the Bool instances, but the Bool instances are quite complicated; it would be at least as ugly as manually deriving an Unbox instance for vectors. Unlike vectors, you also can't just derive Storable and use

I know its a very basic question but I want to be clear about the concept. I want to know how == operator works in case of primitive and object type. For example Integer a = 1; int b = 1; System.out.println(a == b) how a is compared with b , whereas a contain the ref of object that contains value 1. Can somebody clearify it to me how it works internally? In general the equality operator in Java performs a so called shallow comparison. In other words it compares the values that variables contains. Now the variables of primitive data types contains the value itself while the reference types

I'm aware that boxing and unboxing are relatively expensive in terms of performance. What I'm wondering is: Does passing a value type to a method's out parameter cause boxing/unboxing of the variable (and thus a performance hit)? Can the compiler optimize this away? int number; bool result = Int32.TryParse(value, out number); As others have pointed out, there's no boxing here. When you pass a variable as an argument corresponding to an out or ref parameter, what you are doing is making an alias to the variable . You are not doing anything to the value of the variable. You're making two

To put it in code - which has better performance (if there is a difference at all)? Given this: public class Customer { .... public Boolean isVIP(){...} ... } Which is faster? public void handleCustomer(Customer customer) { if (customer.isVIP()) // Auto Unboxing { handleNow(customer); } else { sayHandlingNowButQueueForTomorrow(customer); } } or this: public void handleCustomer(Customer customer) { if (customer.isVIP().booleanValue()) // Explicit unboxing { handleNow(customer); } else { sayHandlingNowButQueueForTomorrow(customer); } } Mark D No difference between them, you can verify it in the

The .NET 1.0 way of creating collection of integers (for example) was: ArrayList list = new ArrayList(); list.Add(i); /* boxing */ int j = (int)list[0]; /* unboxing */ The penalty of using this is the lack of type safety and performance due to boxing and unboxing. The .NET 2.0 way is to use generics: List<int> list = new List<int>(); list.Add(i); int j = list[0]; The price of boxing (to my understanding) is the need to create an object on the heap, copy the stack allocated integer to the new object and vice-versa for unboxing. How does the use of generics overcome this? Does the stack

Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html "If your program tries to autounbox null, it will throw a NullPointerException." javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time,

struct Point { public int x; public int y; } void Main() { Point p; p.x = 1; p.y = 1; Object o = p; ((Point) o).x = 4; // error ((Point) o).x = 5; // error ((Point) o).x = 6; // error p = (Point) o // expect 6 } Why doesn't it compile to ldloc.1 // o unbox Point ldc.i4.4 stfld Point.x Where C++ CLI allows it. For those who don't know, unbox is not required to create a copy of value types , instead it pushes a pointer to the value on to the stack. Only assignment would create a copy. Because of how value types work, the boxed Point is a copy of the original, and "unboxing" it by casting back to