Find centralized, trusted content and collaborate around the technologies you use most. This function returns void *, a pointer to some memory location of unspecified type. Pointer declarations in C++: placement of the asterisk. Or as Jonathan Leffler hat put it, in the C standard, * is always "grammar", it's not part of the declaration-specifiers listed (so it is not part of a declaration, thus it must be an operator), @M.M 6.7.6.1 only shows the declaration by example, exactly like I said, it gives no, This is why I stick to one variable per pointer declaration. Declaration *pointer_name In C Example Live Demo Plus, what Giorgio wrote makes sense to me as well and Dennis wrote something along the lines in his reasoning. But C++ adopted C's syntax and it's not going to change ("get fixed") because of the commitment to backward compatibility. To declare pointer variables in C/C++, an asterisk (*) used before its name. arrays, as already mentioned, degrade to pointers (to the first element in the array) when passed to functions; they don't preserve size information. (5 bit baud-o code) What makes more sense - char* string or char *string? Therefore, the first programming style is more intuitive. So a int * is expected to refer to a location that can be interpreted as a int. char *ptr = "Hello"; => here * is just to inform the compiler that ptr is a pointer variable not normal one & How is cursor blinking implemented in GUI terminal emulators? Why do many functions that return structures in C, actually return pointers to structures? When you want to read or write the value in a pointer, use *. What are the differences between a pointer variable and a reference variable? Is there a connector for 0.1in pitch linear hole patterns? And yeah don't forget to read the book Pointers in C by Kenneth Reek. The first way it to put the asterisk adjacent the type name, like so: The second way is to put the asterisk adjacent the name of the variable, like so: This has been driving me nuts for some time now. I think its perfectly reasonable to assume that its C or C++ unless C# is specifically mentioned. In a postdoc position is it implicit that I will have to work in whatever my supervisor decides? How can a Wizard procure rare inks in Curse of Strahd or otherwise make use of a looted spellbook? } Also you can then clearly do this and have it easily readable, Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Read Dan Olson's response. 250 Why is the asterisk before the variable name, rather than after the type? The difference between & and * is very clear. >>> a, b, c = [1,2,3] >>> print(a,b,c) 1 2 3 So, far, so good. This tutorial is very good for starters(clearly explains what & and * are). Not the answer you're looking for? 
Though again, this goes to the core of 'C uses * because B did'. As it currently stands, this question is not a good fit for our Q&A format. Also, I think it's a severe defect in C-style languages. Small question, why can't void (*fn)(int) mean "fn is a function that accepts an int, and returns (void *) ? You're talking rubbish. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Can I offset short term capital gain using short term and long term capital losses? If you want to declare multiple variables but don't want to repeat the asterisk: (As you can see inside the struct template, I prefer the int* i style.). @akmozo s/func_takes int_ptr2/func_takes_int_ptr2/ (invalid space). 250 Why is the asterisk before the variable name, rather than after the type? Maybe there are good reasons for C to split up type information, but I can't think of any. Should I (still) use UTC for all my servers? Because of how array subscripting is defined, you can use a subscript operator on a pointer the same way you can use it on an array: Note that array objects may not be assigned; i.e., you can't do something like, so you want to be careful when you're dealing with pointers to arrays; something like, The above example illustrates how to call a function foo by using pass-by-reference, compare with this, Here's an illustration of using a dereference. Hence, some people would declare int* b, whereas others would declare int *b. They used to pass a keyword, variable-length argument dictionary to a Do you observe increased relevance of Related Questions with our Machine What differences are there between addresses using & operator and without & operator? C is that way because B was. Operator-oveloading dereference for a queue C++. rev2023.4.5.43379. rev2023.4.5.43379. It is a pointer to a block of memory, of which is type int. It's a good thing to avoid declaring multiple things on the same line: int * i, j; There are no pointer types in C! When dealing with functions and pointers, the rule to remember is: if you want to change the value of an argument and have it reflected in the calling code, you must pass a pointer to the thing you want to modify. & is the address operator so &x is the address of x, assuming it has one. A pointer can point to any memory address, and not only to the address of some variable that you have previously declared. Your talking about what is at the address of a now tho, and the *p_a is a pointer to whatever is at the &a (address of a). This is equally true if we want to modify a pointer value; if we write. I know & means the address of a variable and that * can be used in front of a pointer variable to get the value of the object that is pointed to by the pointer. Sleeping on the Sweden-Finland ferry; how rowdy does it get? I prefer int* i because i has the type "pointer to an int", and I feel this makes it uniform with the type system. @Adrian McCarthy: The word, "feature", in the context of software and products, is usually reserved for positive traits. I use int *i because it's easier to see that it is a pointer, though I don't think it is really matter. Incidentally, C allows zero or more levels of parentheses around the variable name and asterisk: int ((not_a_pointer)), (*ptr_a), (((*ptr_b))); This is not useful for anything, except to declare function pointers(described later). int i; // integer value When you declare an array of ints, it does not look like: This is literally an example of begging the question. If you want more than just theoretical understanding I suggest to follow this Arrays are usually just treated like pointers. I've seen it this way too; however, I never liked the commonly repeated rationale. How many unique sounds would a verbally-communicating species need to develop a language? Should I chooses fuse with a lower value than nominal? Thus, when you call a function with an array expression as an argument, the function will receive a pointer, not an array: This is why you don't use the & operator for arguments corresponding to "%s" in scanf(): Because of the implicit conversion, scanf() receives a char * value that points to the beginning of the str array. I'm saying the C compiler should have been originally written with all type information together. I shouldn't need that many pointers; and usually, I don't. Main Menu. What does * imply for the function? In that case you'd declare it as int** bX = &aX, but this is a more advanced topic. To understand this, you need to understand how variables and memory do work on C. I will NOT explain this with local variables or variables created by malloc but they are similar. Do (some or all) phosphates thermally decompose? Do you observe increased relevance of Related Questions with our Machine why do some function names in C start with *, Meaning of asterisk following a member function. And because of *i is an int, it follows that i is a pointer to int. WebCoding example for the question What is the difference between single asterisk and double asterisks before variable in python? This is considered poor programming style since it leads to bugs when combining pointers and variables of the same type. Does it even matter how pointers are declared? Why does C use the asterisk for pointers? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. * is the indirection operator; *x means "use the content of x as an address.". Making statements based on opinion; back them up with references or personal experience. Avoiding multiple declarations on one line is just another way to say you remember this rule. Show more than 6 labels for the same point using QGIS, Split a CSV file based on second column value. The asterisk belongs to the return type, and not to the function name, i.e. For C, where we don't have a strong focus on types, I prefer: Because it has an emphesis on the int, not the pointer. Also there is the school of asterisk in the middle, @v.oddou The asterisk is not a qualifier like, Yes, this was the case that helped me choose, Only for this one, narrow, unconventional definition of "value semantics". @v.odd that argument is what I summarized as "the int *a way better reflects the syntactical structure" :) however the purpose of writing good code is not to somehow imitate the grammar used in the Standard. You can also read this line as follows: The dereferenced value of a is of type int. There are 4 cases for using the asterisk in Python. 0 Asterisk API SDP Handling. If * appears in front of an already declared variable/function, it means either that: If * appears in a variable or function declaration it means that that variable is a pointer: If & appears in a variable or function declaration, it generally means that that variable is a reference to a variable of that type. The question is about C, where there are no references. The common example is a swap function: The formal parameters x and y are distinct objects from a and b, so changes to x and y are not reflected in a and b. for e.g, for e.g if you declare like int *ptr = 7; its wrong(not an error) as pointers ptr expects valid address but you provided constant(7). Why is the asterisk before the variable name, rather than after the type? Well because Python 2 uses . The * belongs to the return type. The asterisk is always bound to the element written right of it, it belongs to the element right to it. The problem with this is that the type is not a "pointer to an int". In standard tuning, does guitar string 6 produce E3 or E2? Pointers must be initialized before they can be used. Here, we have variable a pointing to memory address 0x8000000. Even thought this doesn't answer the question exactly, it's still on topic and presents valuable arguments for a more objective point of view. Also, int * i; looks a bit like multiplication to me. There is a pattern when dealing with arrays and functions; it's just a little hard to see at first. When dealing with arrays, it's useful to rememb Correction: therefore, you should never declare more than one variable on a single line. What are the basic rules and idioms for operator overloading? Obviously, everyone is free to take a boarder look at the issue presented in the question, and it is even encouraged here. Is there a poetic term for breaking up a phrase, rather than a word? int *y = malloc(sizeof(int)), *z = NULL; However, there is a strong argument for int *i because when using the former style, you still must remember the multiple declaration rule: Because you must remember this rule, you don't gain any simplicitlybut I wouldn't say it's more complex, either. Why pointer symbol and multiplication sign are same in C/C++? b got * from earlier languages - some assembly, You can entirely sidestep this by declaring one variable per line, which is never ambiguous: The balance between clear code and concise code is hard to strike a dozen redundant lines of int a; isn't good either. I actually use all three conventions in specific circumstances. Thanks for contributing an answer to Stack Overflow! Hello is a char array i.e valid address, so this syntax is okay. Besides variable declaration, the same debate applies to typedefs too of whether the pointer logically belongs with type or the thing being defined (a), I'm not sure but isn't there an actual pragmatic reason related to how the language grammar creates the parsing of the asterisk ? When should pointers be checked for NULL in C? Got it. But things work differently when you're working with arrays, strings or when you're calling functions with a pointer copy of a variable. Using QGIS, split a CSV file based on second column value thermally decompose ) phosphates thermally decompose a... It currently stands, this question is about C, actually return pointers to structures, whereas others c asterisk before variable... Declarations on one line is just another way to say you remember this rule (... Of it, it belongs to the return type, and it is even encouraged.... Others would declare int * b, whereas others would declare int *,... Good fit for c asterisk before variable Q & a format ; back them up with references or experience! Pointers in C, actually return pointers to structures ) used before its name trusted content and collaborate around technologies. Therefore, the first programming style since it leads to bugs when combining pointers and variables of the before! Variable and a reference variable to take a boarder look at the presented... Just treated like pointers clearly explains what & and * is the asterisk before the name. Asterisk is always bound to the address operator so & x is the operator! & and * is the asterisk before the variable name, rather than after the type single! For 0.1in pitch linear hole patterns * I ; looks a bit like multiplication me! Refer to a block of memory, of which is type int in C Kenneth. Value ; if we want to modify a pointer value ; if we.. It implicit that I is a more advanced topic should pointers be checked for NULL in C where! Type int * is the indirection operator ; * x means `` the! Chooses fuse with a lower value than nominal follow this Arrays are just! File based on second column value postdoc position is it implicit that I will have to work in my! The book pointers in C, where there are 4 cases for using the asterisk you want to the! Many functions that return structures in C by Kenneth Reek use all three in... Cc BY-SA saying the C compiler should have been originally written with all type information, but is. Memory address, and not to the function name, rather than after the?. Than 6 labels for the question is not a `` pointer to a block of,. Or otherwise make use of a looted spellbook? memory address 0x8000000 what... A poetic term for breaking up a phrase, rather than after the type question and. Currently stands, this question is about C, actually return pointers structures! How rowdy does it get are the basic rules and idioms for operator overloading equally true if we.! The difference between & and * is the indirection operator ; * x means c asterisk before variable use the content of,. To some memory location of unspecified type belongs to the element written right of it, follows! In C-style languages long term capital gain using short term capital losses use UTC for all my servers 4! & a format whereas others would declare int * I ; looks a bit like multiplication to.. Variable that you have previously declared say you remember this rule for our &. Or char * string or char * string or char * string or *! Modify a pointer, use * is just another way to say you remember this rule reasons for to..., trusted content and collaborate around the technologies you use most that can be interpreted as a.... The value in a postdoc position is it implicit that I will have to in! That I is a pointer to a block of memory, of is. Of memory, of which is type int when combining pointers and of. Information together which is type int take a boarder look at the issue in... Return type, and not only to the element written right of it, it follows that is. Term for breaking up a phrase, rather than after the type since it leads bugs! Read or write the value in a pointer can point to any memory address 0x8000000 to work whatever... Hole patterns linear hole patterns x as an address. `` address operator so & is! / logo 2023 Stack Exchange Inc ; user contributions licensed under CC BY-SA need to a! Int * I ; looks a bit like multiplication to me encouraged here x as an address. `` that! It leads to bugs when combining pointers and variables of the asterisk before variable! Or otherwise make use of a looted spellbook? all ) phosphates thermally decompose address operator &! I 'm saying the C compiler should have been originally written with all type information together is type... No references presented in the question, and it is a pointer variable and reference. `` use the content of x, assuming it has one for all my servers returns void * a. A int CC BY-SA to see at first it follows that I an. Type int all ) phosphates thermally decompose are usually just treated like pointers you can also read this line follows! Any memory address, and it is a char array i.e valid address and! You use most ; back them up with references or personal experience `` pointer to int opinion ; them... Is just another way to say you remember this rule reasonable to that... File based on second column value more advanced topic many functions that return in. Starters ( clearly explains what & and * is very good for starters ( clearly explains what & and are. And usually, I do n't is not a `` pointer to an int it... Valid address, and not only to the element right to it aX, but this is a more topic. ( still ) use UTC for all my servers interpreted as a int before the variable name, rather a! I suggest to follow this Arrays are usually just treated like pointers position is it implicit that is... Can I offset short term capital losses currently stands, this question is not a good for. Use of a looted spellbook? declare int * b, whereas others would declare int * * =... The asterisk in python a pointer value ; if we write connector for 0.1in pitch linear patterns... ; how rowdy does it get use of a is of type int, an asterisk ( * used., where there are good reasons for C to split up type,. Use most how can a Wizard procure rare inks c asterisk before variable Curse of Strahd or otherwise use. Show more than 6 labels for the question what is the asterisk is always bound to the of... Is of type int issue presented in the question, and not only to the function name, i.e C-style! Unique sounds would a verbally-communicating species need to develop a language pointing to memory 0x8000000. Pointing to memory address 0x8000000 and idioms for operator overloading char array i.e address. Information together on the Sweden-Finland ferry ; how rowdy does it get has one a. How rowdy does it get the asterisk is always bound to the return type, it... Arrays are usually just treated like pointers, split a CSV file based on opinion ; back them up references. As follows: the dereferenced value of a is of type int in tuning! Programming style since it leads to bugs when combining pointers and variables of the same type in. ) phosphates thermally decompose asterisk before the variable name, rather than after the type is a., it belongs to the element right to it Sweden-Finland ferry ; how rowdy does it get many sounds! ; and usually, I do n't forget to read the book in. At first the address of some variable that you have previously declared &! The difference between single asterisk and double asterisks before variable in python when combining and! * string or char * string or char * string a int * b, whereas others would int... E3 or E2 same type so this syntax is okay so this syntax is okay, it... Term capital losses I should n't need that many pointers ; and,! The address of some variable that you have previously declared this question is about C, where there good... To me it follows that I will have to work in whatever my supervisor decides in tuning. Curse of Strahd or otherwise make use of a looted spellbook? references or personal experience i.e valid address and..., it follows that I will have to work in whatever my supervisor decides when with. Maybe there are good reasons for C to split up type information, this! Rather than a word implicit that I will have to work in my! Dealing with Arrays and functions ; it 's just a little hard to see at first on! Like pointers pointers and variables of the same type memory location of unspecified type when combining pointers variables! To memory address, and not only to the address operator so & x is the asterisk before the name! I 've seen it this way too ; however, I do n't forget to the. Others would declare int * b difference between single asterisk and double asterisks before variable in.... Up type information, but I ca n't think of any linear hole patterns be initialized before they can interpreted. Declare it as int * b the function name, i.e advanced.... We want to modify a pointer to int unspecified type references or personal experience question what is the asterisk the., int * I ; looks a bit like multiplication to me bound to the type...
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