Feb 09, 2011 The method using an if statement is considerably faster than the null coalescing operator when x is already not null. The difference when x is not null looks like it might be due to the null coalescing operator assigning the value of x back to x (stfld in IL), whereas the null check jumps over the stfld instruction when x is not null. This C# example program shows how to handle null List references.
At the very high level, we can think of NULL as null pointer which is used in C for various purposes. Some of the most common use cases for NULL area) To initialize a pointer variable when that pointer variable isn’t assigned any valid memory address yet.b) To check for null pointer before accessing any pointer variable. By doing so, we can perform error handling in pointer related code e.g. Dereference pointer variable only if it’s not NULL.c) To pass a null pointer to a function argument when we don’t want to pass any valid memory address.The example of a) is.
FilternoneBy specifically mentioning NULL pointer, C standard gives mechanism using which a C programmer can use and check whether a given pointer is legitimate or not. But what exactly is NULL and how it’s defined? Strictly speaking, NULL expands to an implementation-defined null pointer constant which is defined in many header files such as “ stdio.h”, “ stddef.h”, “ stdlib.h” etc. Let us see what C standards say about null pointer. From C11 standard clause 6.3.2.3,“ An integer constant expression with the value 0, or such an expression cast to type void., is called a null pointer constant. If a null pointer constant is converted to a pointer type, the resulting pointer, called a null pointer, is guaranteed to compare unequal to a pointer to any object or function.”Before we proceed further on this NULL discussion:), let’s mention few lines about C standard just in case you wants to refer it for further study.
Please note that ISO/IEC 9899:2011 is the C language’s latest standard which was published in Dec 2011. This is also called C11 standard. For completeness, let us mention that previous standards for C were C99, C90 (also known as ISO C) and C89 (also known as ANSI C). Though the actual C11 standard can be purchased from ISO, there’s a draft document which is available in public domain for free.Coming to our discussion, NULL macro is defined as ((void.)0) in header files of most of the C compiler implementations.
But C standard is saying that 0 is also a null pointer constant. It means that the following is also perfectly legal as per standard. FilternonePlease note that 0 in the above C statement is used in pointer-context and it’s different from 0 as integer. This is one of the reason why usage of NULL is preferred because it makes it explicit in code that programmer is using null pointer not integer 0. Another important concept about NULL is that “ NULL expands to an implementation-defined null pointer constant”.
This statement is also from C11 clause 7.19. It means that internal representation of the null pointer could be non-zero bit pattern to convey NULL pointer.
That’s why NULL always needn’t be internally represented as all zeros bit pattern. A compiler implementation can choose to represent “null pointer constant” as a bit pattern for all 1s or anything else. But again, as a C programmer, we needn’t to worry much on the internal value of the null pointer unless we are involved in Compiler coding or even below level of coding.
C++ Not Null
Having said so, typically NULL is represented as all bits set to 0 only. To know this on a specific platform, one can use the following. FilternoneMost likely, it’s printing 0 which is the typical internal null pointer value but again it can vary depending on the C compiler/platform. You can try few other things in above program such as printf(“‘%c“,NULL) or printf(“%s”,NULL) and even printf(“%f”,NULL). The outputs of these are going to be different depending on the platform used but it’d be interesting especially usage of%f with NULL!Can we use sizeof operator on NULL in C? Well, usage of sizeof(NULL) is allowed but the exact size would depend on platform.
C# Initialize List Of Strings
FilternoneOn some machines, the above would compile successfully but crashes when the program is run though it needn’t to show the same behavior across all the machines. Again it depends on lot of factors.
But the idea of mentioning the above snippet is that we should always check for NULL before accessing it.Since NULL is typically defined as ((void.)0), let us discuss a little bit about void type as well.
An object and collection initializer is an interesting and very useful feature of C# language. This feature provides a different way to initialize an object of a class or a collection. This feature is introduced in C# 3.0 or above. The main advantages of using these are to makes your code more readable, provide an easy way to add elements in collections, and mostly used in multi-threading. Object Initializer in C#In object initializer, you can initialize the value to the fields or properties of a class at the time of creating an object without calling a. In this syntax, you can create an object and then this syntax initializes the freshly created object with its properties, to the variable in the assignment. It can also place indexers, to initializing fields and properties, this feature is introduced in C# 6.0.Example: In the below example, Geeks class doesn’t contain any constructor, we simply create the object and initialize the value at the same time using curly braces in the main method. Yakusoku no neverland manga.
This initializing of values is known as object initializer. Output:Author Name: Ankita SainiAuthor Id: 102Total no of articles: 178Note: When the compiler compiles the above program it assigne the values to the object as shown below:Geeks geeks = new Geeks;geeks.authorname = 'Ankita Saini';geeks.authorid = 102;geeks. Totalarticle = 178;Geeks obj = geeks;Collection Initializer in C#Collection initializer is also similar to object initializers.
C# Initialize List With Null
The collections are initialized similarly like objects are initialized using an object initializer. Or in other words, generally, we used the Add method to add elements in collections, but using a collection initializer you can add elements without using Add method.Example.