How would the CLR access them compared to instance variables. Just check for nullptr, and only create instance on heap first time. From the standard, section 6.2.4/3 Storage durations of objects: An object whose identifier is declared without the storage-class specifier _Thread_local, and either with external or internal linkage or with the storage-class . I understand exactly what you are talking about and it has nothing Use an instance variable---no static declaration---to The vars of the method are out of scope and elegible for GC, but here's this static method with local vars that are still referenced. "Declaring a static variable outside of the scope that tracks how many time a method is called will result in totaling up the method calls for all of the objects of that type, not just the single instance. But I'm not talking about global variables at all. Beides, a private static member cannot be accessed by derived classes anyway. What purposewould a local static variable serve? In 'C', static local variables are global variables with a limited scope. the static variables initialized only once and it . Do the parentheses after the type name make a difference with new? Beides, a private static member cannot be accessed by derived classes anyway. Do bracers of armor stack with magic armor enhancements and special abilities? The OPasked abouta local static variable, per instance. Thank-you. "Fooling computers since 1971.". Not the answer you're looking for? Thisthread was a question, not a discussion. How does that help anything? So you can have 2 local static . static int x = 0; return (x++); } Write the definition of a function named alternator that receives no parameters and returns true the first time it is invoked, returns false the next time it is invoked, then true , false and so on, alternating between true /false on successive invocations. But it should also be local to the function that uses it. Are defenders behind an arrow slit attackable? Actually in VB, since it calls "static" members "Shared", static locals can be called "Static", which actually existed in VB 6.0: http://msdn.microsoft.com/en-us/library/aa266296(VS.60).aspx. variables with limited visibility.) I already said this over a year ago, but regarding implementation/storage: a static local variable in an instance method would simply be an instance field, only invisible outside the method; and a static local variable in a static method would simply be When to implement a static local variable as a hidden instance field or a hidden static field? 6.10 Static local variables. Thanks for contributing an answer to Stack Overflow! So I ask again, what purpose wouldhaving static variables per instanceserve? be my guest trying to debug the code when it does not work. My opinion is that both private fields and static local variables can be useful. per instance be stored? That is not what the thread is about. He didn't ask how YOU write code, he asked how to do static locals The feature was omitted from C# by design. In my specific case right now I have a method that gets called numerous times. For example, consider the below function. to do with what the original poster asked about and was looking for. You would normally use a static variable in cases where you wish to preserve the value of a variable inside a function. But see, in the first place you name this field in a self documenting way, to let it be known that it's to be used by that method alone. Prefixtablenameswithdefaultschemaname if set, //staticregexdefinedabove. Ready to optimize your JavaScript with Rust? Hence it should be a static local variable. I do not see howthis offers any advantages over what is currently available. There should be no reason for their lack of existance. You are asking for global variables. Static variables are stored in initialised data segments. Expressing the frequency response in a more 'compact' form. Assuming the initialization does not use other variables, is there any difference between preserving the value between calls, and setting the same constant value each call? Code is code, there is no proper or improper. #include <iostream> using namespace std; void increase() { static int num = 0; cout << ++num << endl; } int main() { increase(); increase(); return 0; } Output: 1. But (besides the doubtfully preferable possibility of using another keyword): Another small question, is a volatile var likely be registered? A normal or auto variable is destroyed when a function call where the variable was declared is over. In 'C', static local variables are global variables with a limited scope. We can't let lack of imagination or thinking too far inside of the box limit development. Finally, VB allows them, and its C/C++ common practice. Myself I would like them introduced in a future C# version. What we're talking about is the exact same thing that other languages like C++ and D have. Question 1: Describe, how can we make a local variable global in the C++ language?. Should I give a brutally honest feedback on course evaluations? That's data hiding one step forward. You cannot start moving type objects around in memory to allow them todynamically allocate and deallocate static variables per instance. The relevant section is 6.7.4, see e.g. Static local variables: variables declared as static inside a function are statically allocated while having the same scope as automatic local variables. is waste of time. Aside fromthe fact that it goes completely against the grain ofhow the CLR currentlyworks, what purpose would that featureserve? Should teachers encourage good students to help weaker ones? One of us is misunderstanding the other. Now, I can see how this can be a huge burden for garbage collection. Most variables stored in the array (i.e., in main memory) are larger than one byte, so the address of each variable is the index of the first byte of that variable. But that clutters the method signature with "unnecessary" housekeeping, and it needs to be duplicated if calling from somewhere else. If you lack the discipline to reference a static variable in your code from only a single location or method, then I do not know what to say. VB.Net static local variables are not thread safeStatic variables are not used very often but they can be very useful when used in the correct way.Variables do have a lifetime.Indicates that the local variable is preserved between calls.A static variable can be thought of as a local variable with memory.A static variable is a local variable whose lifetime is the lifetime of the entire module and not the procedure where it is declared.In fact static variables retain their values as long as the code module is active. Why do quantum objects slow down when volume increases? Central limit theorem replacing radical n with n. Why would Henry want to close the breach? static variable per instance. Is there a higher analog of "category with all same side inverses is a groupoid"? Difference between static, auto, global and local variable in the context of c and c++. Memory Layout of C program. And if that restriction exists just because people keep asking "why would What purposewould a local static variable serve? The vars of the method are out of scope and elegible for GC, but here's this static method with local vars that are still referenced. How does that help anything? you want to do that? There are many applications for this but without the functionality we tend to code around it. Plenty of other object-oriented languages support Just because you don't see the benefit of a particular feature, or you view it as "bad" doesn't For example, 'a' is of type char with a value 97 on an ASCII based system.A character or a string of characters together in double quotes represent a string literal. The rubber protection cover does not pass through the hole in the rim. @iBrAaAa ? variable, but now it has to check if the variable is an instance variable or a static variable, which would slow the CLR down when it accessed instance variables because of the additional check. It's only the compiler that would have to be aware that static local variables have the same scope that fields, but visibility limited to one method.". This is not the only post the OP made at the time. When there is a conflict between the global variable and local variable, the local variable gets the precedence, that . C/C++ The purpose of static const local variable [closed]. rev2022.12.11.43106. Actually even from the point of view of OOP, or rather data hiding, which is supposedly something aimed at by OOP, allowing this would mean stronger data hiding than disallowing it. That's data hiding one step forward. (2) the compiler guarantees that static local variable initialization will only be executed once and all subsequent calls to this function will skip re . You cannot start moving type objects around in memory to allow them todynamically allocate and deallocate static variables per instance. Use an instance variable---no static declaration---to Also known as Static method variables or method level static variablesThese are not supported in C#.The equivalent in C# would be a private static variable to the class. have its internals isolated from callers, so should a method. Where variables are stored? That individual made a snide remark of their own. You make a bolder statement to whoever reads the code later: this won't ever change. be my guest trying to debug the code when it does not work. But that clutters the method signature with "unnecessary" housekeeping, and it needs to be duplicated if calling from somewhere else. have its internals isolated from callers, so should a method. Well I do. Tabularray table when is wraped by a tcolorbox spreads inside right margin overrides page borders. There are tons of features in C# that are not strictly "object-oriented". Obviously, they would have to be stored in some fashion on the Managed Heap with the object instance, in a fashion identical to an instance variable. For the compilers it's a very small change. Rather than negating the OPs question, you can just say, "C# doesn't support it, unfortunately" instead of "You should be writing code the way that I write it." For help clarifying this question so that it can be reopened, Not the answer you're looking for? Just as a class should When you put const, you don't just mean the compiler shouldn't let you modify the variable. Global variables are automatically initialized at the time of initialization. Use an instance variable---no static declaration---to track calls on just a single instance. In this scenario the "static" keyword has different meanings (just like for example "using" currently Prefixtablenameswithdefaultschemaname if set, //staticregexdefinedabove. B. We do not currently allow content pasted from ChatGPT on Stack Overflow; read our policy here. It woulddiscarded when the method completes. Internal Static Variables: Internal Static variables are defined as those having static variables which are declared inside a function and extends up to the end of the particular function. Thus the compiler must emit code to guess . This is why old threadsare bestleft alone, The problem will turn into a murder mystery, a "whodunit.". If it's not possible, it's not possible, and you can offer alternatives, but insulting someone by claiming they don't have the discipline to do something makes you look like an arrogant dickwad. be an static field, invisible outside the method.". For example how many times the method was called on any of the class objects. And then you browse the members of your class, and the list is clogged by half of them that are state private fields used by one method alone each, that should be static local variables, not appearing in the list of class members. Is there a difference in the lifetime of the Singleton between A and B? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Static locals would obviously be useful to at least some people. I just want others to see both sides too. Connect and share knowledge within a single location that is structured and easy to search. In C and C++, what is the advantage of making a local const variable static? Anyway, I rather dislike when people say "why wouldwant to do that?" This is not the only post the OP made at the time. A local static variable is a variable that can maintain its value from one function call to another and it will exist until the program ends. What I'm talking about is like a class member, but with even more restricted visibility. You could always use one of the hallmarks of OOP and encapsulate such a method within its' own class. The term static is one of the most confusing terms in the C++ language, in large part because static has different meanings in different contexts. In the heap case, you do not want to create a new instance on the heap every time. You seem to be the one misunderstanding the issue (no offense meant). (1) the compiler guarantees that. A local variable in a function or static local variable: Visibility is the same as the automatic local variables. Mathematica cannot find square roots of some matrices? Difference between static class and singleton pattern? The content you requested has been removed. You can use variables a and b inside any function. Well depending on whether the method it's declared in, is instance or static. When a local static variable is created, it should be assigned an initial value. Sure, none of this is insurmountable, but we tend to go through these minor contortionsas a matter of coursebecause of a language restriction that we all tend to accept. Also, the compiler can take advantage of that new information and optimize it away in some situations, depending on the specific type you are dealing with. Consider the below program, void test(int x, int y) { int a; } In the above program, a, x and y are local variables. Disconnect vertical tab connector from PCB. Arguing about what other languages do and how it would great to have that feature is an argument that Hence it should be a static local variable. When to implement a static local variable as a hidden instance field or a hidden static field? Use instance fields to store the sate of the object. Making statements based on opinion; back them up with references or personal experience. The CLR memory model would need a major redesign to allow for their creation and storoage. Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_u64 on Intel CPUs. Using "static variables" lets you retain the value of a variable that may go in and out of scope during execution, yet remain valid.A static variable has the scope of a local variable although the lifetime of a module level variable. Other then the location where they are . If static local variables were allowed, they would be better for this purpose, because they would be hidden to the rest of the class, as they should. What it does each time is dependent on what it did the last time, so I'd likea couple Booleans andInt32 indexes topreserve state between invocations. This thread was a question, not a discussion. It's only the compiler that would have to be aware that static local variables have the same scope that fields, but visibility limited to one method.". Did neanderthals need vitamin C from the diet? If you are concerned about inherited types modifying a private static variable declared at the class level, then declarethe class assealed. What purpose would having a localstatic variable,declaredinside of a method, I see no compelling reason why C# should exclude this feature. It's only the compiler that would have to be aware that static local variables have the same scope as fields, but visibility limited to one method. Assuming the initialization does not use other variables, is there any difference between preserving the value between calls, and setting the same constant value each call? I only see it slowing down the CLR because the CLR checks for null prior to accessing an object instance. C# doesn't have a direct substitute, the closest match is adding a static private member to your class. All the static variables that do not have an explicit initialization or are initialized to zero are stored in the uninitialized data segment ( also known as the BSS segment). Why does my stock Samsung Galaxy phone/tablet lack some features compared to other Samsung Galaxy models? It can be used with both variables and functions, i.e., we can declare a static variable and static function as well. The default value of static variable is 0. Improve INSERT-per-second performance of SQLite. Local Variable in C: The local variable is a variable that is declared within a function, block (within curly braces), or function argument. Then again, I ask again, what purpose would having a static variable per instance serve? Static local variables are useful when we want to have only one instance of our object in the local scope, which means all calls to the function will share the same object. This is an old thread, which has been resurrected completely out of its' original context. I see no compelling reason why C# should exclude this feature. But we should ask ourselves if the object is only used within the function or not. If it's not, the value will default to 0. Hmm, that's helpful. static variables are declared by writing the key word static. You are asking for global variables. Ready to optimize your JavaScript with Rust? In C++11 at least, when the expression used to initialize a local static variable is not a 'constexpr' (cannot be evaluated by the compiler), then initialization must happen during the first call to the function. MOSFET is getting very hot at high frequency PWM. Difference between static and shared libraries? non-static.). Languages are languages, not paradigms. A. any differences generally? Not even by a side effect where you give this variable as a pointer to another function. Later replies misunderstood the original issue, including the one that you noted, which also entirelymissed the point of the original question. Where a and b are used only with the main () function because they are local variables declared only . Books that explain fundamental chess concepts. Observe the output in this case. Butnow you have gone off into something elsethat is completely different, nowwe havestatic methods with local static variables. In C++, a character in single quotes is a character literal. Global variable in a module or static global variable: Declared at the top of a program. Kept in a register, no, that would be invalid by the compiler, each access of a volatile variable must be done exactly as the code describes, can not be skipped or eliminated. that already happens with "using" for example; and it's also the case in other languages. Now, I can see how this can be a huge burden for garbage collection. "Declaring a static variable outside of the scope that tracks how many time a method is called will result in totaling up the method calls for all of the objects of that type, not just the single instance. I don't see how this is any different from a class-level Static Incidentally, global variables can be declared in IL. If you wish for other code to be able modify it while your method executes, be my guest So, given that the CLR can support But (besides the doubtfully preferable possibility of using another keyword): static data_type var_name = var_value; Following are some interesting facts about static variables in C. 1) A static int variable remains in memory while the program is running. trying to debug the code when it does not work. I ask again, what purpose would having a static variable per instance serve? and nowobject instantiation (if we're notusing static methods)in addition to the method invocations. C++ Primer says. As mentioned in the question, in C++11 both: (1) and (2) you mentioned are guaranteed by the compiler. There's a major problem with local static variableswithin a method. CGAC2022 Day 10: Help Santa sort presents! Were sorry. Actually even from the point of view of OOP, or rather data hiding, which is supposedly something aimed at by OOP, allowing this would mean stronger data hiding than disallowing it. The only possibly arguable downside, is the confusion between the two different meanings the keyword "static" would have, when used in declaring local variables, and elsewhere. Mark the best replies as answers. So a local static variable is really not a local variable at all. static member). I don't see the problem or the need. class, even private, is what could be seen and modified while the method is not yet done, and would pose the very problem you mention. You seem to be the one misunderstanding the issue (no offense meant). They could be allowed in any .NET language, which must compile to IL, and it would need no re-design whatsoever of the CLR. Static in C. Static is a keyword used in C programming language. C# doesn't have a direct . Normal local variables are destroyed when the function completes and recreated/instantiated when the function is called. If they are local variables, then their value persists when execution leaves their scope. serves no purpose. However, the value of the static variable persists between two function calls. 1. "I already said this over a year ago, but regarding implementation/storage: a static local variable in an instance method would simply be an instance field, only invisible outside the method; and a static local variable in a static method would simply . Where would these static variables Also, in C++ the auto keyword no longer means automatic storage duration; it now means . Say you have a doSomething() method in your class, and you use a field, say int doSomethingCount to count how many times this one method was called. It contains local and static variable. A global static variable is one that can only be accessed in the file where it is . For example how many times the method was called ona particularobject.Use static fields to store an item of information that is shared by all objects of the same class. These are local to the block, and their default value is always zero. And then you browse the members of your class, and the list is clogged by half of them that are state private fields used by one method alone each, that should be static local variables, not appearing in the list of class members. It extends until the lifetime of a complete program. ", well, here are reasons why we'd want to do that. A static variable persists, even after end of function or block. That couldrequire a new .cs code module, a duplicate set of'using' statements, Can we keep alcoholic beverages indefinitely? It is possible that a variable can go in and out of scope and yet remain valid during that time (ie keep its value).Once the lifetime of the variable expires the value is lost.It is the lifetime that determines the existence of a variable and it's the scope that determines its visibility.Indicate that the variable is initialised the first time and is then preserved between function / procedure calls.A static variable is a local variable whose life time is the lifetime of the entire module, not just the procedure. Later replies misunderstood the original issue, including the one that you noted, which also entirelymissed the point of the original question. an static field, invisible outside the method. Shraddha. I just edited the question. It is poor OO software design. For example how many times the method was called on any of the class objects. And once compiled they can be implemented as the same thing. In 'C', static local variables are global variables with a limited scope. In C and C++, what is the advantage of making a local const variable static? But, that is not exactly what theOP asked about. and a new one should be started that perhapscontains a link to the old one to provide context for the discussion. It's difficult to tell what is being asked here. Static variables are generally stored in the program's data segment, whereas anything allocated with new will be stored in the heap. (Just like in C static local variables are global To make all local variables in a procedure or function static, place the static keyword at the beginning of the procedure or function heading (eg Static Sub or Static Function). A field of the value Any value to initialize the variable. Anyway, I rather dislike when people say "why wouldwant to do that?" Where would these static variables Their values then persist between invocations. it and the world hasn't ended because of it. we can't just create features without any practical applications either, so I see both sides of this. Plenty of other OO languages support it and the world hasn't ended because of it. this feature, there is no good reason not to have it. Note that the static keyword has various meanings apart from static storage duration. static var - when the class object disposes, How can I fix it? However, in the second case, the variable b was assigned a pointer allocated with new. that is when the method-level static vars can get GC'd. Say you have a doSomething() method in your class, and you use a field, say int doSomethingCount to count how many times this one method was called. and a new one should be started that perhapscontains a link to the old one to provide context for the discussion. The question does not mention any guarantees from the standard. that is when the method-level static vars can get GC'd. Youll be auto redirected in 1 second. I can't do that, I could use a variable with class-level scope (global). track calls on just a single instance.". Just as a class should By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. It goes totally against the grain of theway in which managed memory works. The OPasked abouta local static variable, per instance. 07 Jul. Static global variable is always declared outside the main function, while the static local variable is declared inside the main or any block element (for example inside a function, inside a loop etc. It ought to be a staticlocalvariable. Would salt mines, lakes or flats be reasonably found in high, snowy elevations? I stumbled across this thread because I was specifically looking for a way to make a variable in method static. But, that is not exactly what theOP asked about. variable_name This is the name of variable given by user. in C#. I already said this over a year ago, but regarding implementation/storage: a static local variable in an instance method would simply be an instance field, only invisible outside the method; and a static local variable in a static method would simply be The static variables stay alive till the program gets executed in the end. But thisis sloppy because there's this high level variable (possible several of them or maybe a struct or nested class) which is only there to serve one method. FAQs on Local and Global Variables. Local statics are not destroyed when a function ends; they are destroyed when program terminates. Could a valid C compiler ignore the static? It seems to me that C# has an eclectic design philosophy: if a feature is useful and can be expressed succinctly, it tends to get into the language, even if there may already be a (less convenient) way to do the same thing. ", well, here are reasons why we'd want to do that. variables are normally stored elsewhere, within the class'type object along with the compiled methods. But thisis sloppy because there's this high level variable (possible several of them or maybe a struct or nested class) which is only there to serve one method. Difference between static and shared libraries? The difference between a local static variable and a global variable is the scope: the local variable can be used only inside the function that declares it. One of us is misunderstanding the other. static variable per instance. You can initialize it with an initializer or a static constructor. mean that everyone else does. What it does each time is dependent on what it did the last time, so I'd likea couple Booleans andInt32 indexes topreserve state between invocations. If you wish for other code to be able modify it while your method executes No, the key is the difference between lifetime and visibility, perhaps you're not familiar with static local variables in C. A variable that is discarded when the method completes is a regular local variable, a static local variable would not. 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