Use whichever you require. Erases the specified elements from the container. Is explaining UB considered heresy now? c++ vector erase advances iterator. How hard would it have been for a small band to make and sell CDs in the early 90s? @Tim: Those aren't available in the STL (forgot to emphasize that, now fixed). That is NOT what I like to hear. On the other foot, I won't learn how to use them unless I do. Decrement the iterator after it is passed to the erase() but before erase() is executed. Thank you for your valuable feedback! You can create an is_odd predicate: Thanks for contributing an answer to Stack Overflow! How can I land without any propulsion? Is it safe to use std::vector.erase(begin(), end()) or std::vector.erase(begin(), begin())? Does the word "man" mean "a male friend"? An iterator pointing to the new location of the element that followed the last element erased by the function call. It was originally solved with std::string::find_last_of, yet I research an alternative way with std::reverse_iterator. @sje397: Added an explanation of why the crash occurs, so people don't get thrown off. Asking for help, clarification, or responding to other answers. Why sponsor the ETL? How to find the memory used by any object, Erasing() an element in a vector doesn't work. This technique is commonly known as the Erase-remove idiom. Connect and share knowledge within a single location that is structured and easy to search. However, erase returns a new iterator that points to the element immediately after the element(s) that were erased (or to the end if there is no such element). @Nim and @Jan Hudec: Actually, the erasing happens (relatively) rarely, and the most common operators on it are iteration over the lot, and random access, which is why I chose vector; unless there is a superior alternative? Why do you want to create pointers of Player? However unless I am missing something the correct statement is (++ri).base(), meaning you 'increment' the reverse_iterator (not the iterator). Why did banks give out subprime mortgages leading up to the 2007 financial crisis to begin with? Instead, if the map is commonly used with reverse iterators, change the comparison operator to gt instead. I would also prefer to avoid some other similar way to separate the erasing the process from the updating loop. No votes so far! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Is it common practice to accept an applied mathematics manuscript based on only one positive report? @Jan Hudec: no You could have a second list, and iterate it; or do it like MSalters suggest. Which kind of celestial body killed dinosaurs? Then again, without knowing them too well, I'll end up using them incorrectly. Making statements based on opinion; back them up with references or personal experience. Perhaps I did not make it clear enough, but I stated in my last paragraph that I'd like to find a solution OTHER than that. @LefterisE That's not a cast. Asking for help, clarification, or responding to other answers. How to call erase with a reverse iterator Ask Question Asked 13 years, 6 months ago Modified 6 days ago Viewed 92k times 237 I am trying to do something like this: for ( std::list< Cursor::Enum >::reverse_iterator i = m_CursorStack.rbegin (); i != m_CursorStack.rend (); ++i ) { if ( *i == pCursor ) { m_CursorStack.erase ( i ); break; } } Methodology for Reconciling "all models are wrong " with Pursuit of a "Truer" Model? rev2023.6.12.43490. Using pointers is much more complicated. last Position just beyond the last element removed from the vector. (left rear side, 2 eyelets), Stopping Milkdromeda, for Aesthetic Reasons. Does the policy change for AI-generated content affect users who (want to) Vector erase function not working (simple code), C++ Struct Error No matching function for call 'erase', How to safely erase elements in a std::vector. Why does Tony Stark always call Captain America by his last name? I only want to remove 1 element, thus the 'break;', using 'remove' would get rid of any that match taking longer and not doing what i want. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, because this is just a simplification of the code, i am not trying to delete all the elements in the real code, ok so it first increment and after the incrementation it compares, No, hidayat; your code is trying to delete all elements in the vector one by one. Error in UCCSD(T) Calculation in PySCF for S atom? Asking for help, clarification, or responding to other answers. To learn more, see our tips on writing great answers. @sje Yes; that is correct. Making statements based on opinion; back them up with references or personal experience. This page was last modified on 2 June 2020, at 13:42. Cutting wood with angle grinder at low RPM. What happens is that remove compacts the elements that differ from the value to be removed (number_in) in the beginning of the vector and returns the iterator to the first element after that range. The latest openly available working draft for the standard I could find is for c++11, @HkonEgsetHarnes that is a pre-C++11 draft . ie keeping the current code structure, but using some little-known C++fu to make it work. I think the point is that the parent iterator is invalid sometimes after. Why have God chosen to order offering Isaak as a whole-burnt offering to test Abraham? While this code may answer the question, it is better to explain what it does and add some references to it. How to call erase with a reverse iterator using a for loop. 30-year c++ veteran coming back from C#/Java land after a five year hiatus. What do you gain by writing this code yourself instead of using. because the loop removes all elements of the vector. A reverse_iterator is just an iterator adaptor that reverses the direction of a given iterator. It does not actually remove elements from the container but move all safe elements to the front and returns an iterator pointing to where the end should be, so they can be deleted using a single call to std::erase. Example: erase invalidates r. Dereferening r after that causes undefined behavior. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. I'm unsure of all you're design constraints / goals, but you could expose the need to delete a child through it's public API and just make Parent::update conditionally do the delete. This is the container end if the operation erased the last element in the sequence. Where do I find the current C or C++ standard documents? Since calling the erase() function on the vector element invalidates the iterator, special care needs to be taken while erasing an element. I suppose I could keep the rest of this book-keeping in a separate function and call it before I call child.erase(). The iterator first does not need to be dereferenceable if first == last: erasing an empty range is a no-op. Because the method erase in vector return the next iterator of the passed iterator. How Can I Put A Game Gracefully On Hiatus In The Middle Of The Plot? Connect and share knowledge within a single location that is structured and easy to search. Thanks for contributing an answer to Stack Overflow! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. std::erase_if () replaces the era. Enter your email address to subscribe to new posts. And make sure that you properly handle the case where vector is empty. This might work out faster for you if you're using a std::vector, where erasing in the middle of the contents can involve a lot of copying or moving. Problem deploying smart contract on rococo. is there a way to convert a reverse iterator to a regular iterator or another way to remove this element from the list? You have a vector of pointers but you don't attempt to free the memory that the pointers point to. vectordequeerase mapseterase it++ If you do, funny things can happen. Your iterator is going to point to that memory with the offset to the element you want. See, The code in this answer is wrong, erasing an item from a vector invalidates all iterators at the point of the erase and later (which includes, kera.name/articles/2011/06/iterator-invalidation-rules-c0x, open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf, en.cppreference.com/w/cpp/container/vector/erase, How to keep your new tool from gathering dust, Chatting with Apple at WWDC: Macros in Swift and the new visionOS, We are graduating the updated button styling for vote arrows, Statement from SO: June 5, 2023 Moderator Action. detect if zone transfer with dig succeed or not via return code. Where can one find the aluminum anode rod that replaces a magnesium anode rod? rev2023.6.12.43490. Find centralized, trusted content and collaborate around the technologies you use most. std::pmr::vector is an alias template that uses a polymorphic allocator You increment it past the end of the (empty) container in the for loop's loop expression. Find centralized, trusted content and collaborate around the technologies you use most. Thats all about removing elements from a vector inside a loop in C++. Where can one find the aluminum anode rod that replaces a magnesium anode rod? One basis for a solution (as others have said) is to switch from std::vector to std::list, since you can then erase nodes from a list without invalidating references to other nodes. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Capturing number of varying length at the beginning of each line with sed. But in the real world, it shouldn't cause any problems unless the implementation intentionally checks iterator validity. Vector erase will not "erase" first element, Delete elements from a vector in C++11 while iterating over it, Remove elements in std::vector, No instance of overloaded function ".erase" matches the argument list. Why did banks give out subprime mortgages leading up to the 2007 financial crisis to begin with? @James But then how above code provided in question is working since erase will invalidate iterators ? This works for me. However, the problem is that Parent::erase() actually needs to do more than simply remove the element from the vector. Simply checking for .end() still leaves a bug though, as you always skip an element on every iteration (it gets 'incremented' by the return from .erase(), and then again by the loop), (for completeness: I assume this is a simplified example, if you simply want every element gone without having to perform an operation on it (e.g. can you call erase on end()? If you add it multiple times, there will only be one instance to erase anyway. Since f.erase(r) does not capture the returned value which would be the new iterator value, and there is no other iterator incrementor, and according to documentation, erase(iterator position) argument is not passed by reference, where does the iterator get advanced? It may appear to work, because that is one possible behaviour. Find centralized, trusted content and collaborate around the technologies you use most. I understand they'll both work, but I usually take the same approach as James, to me it seems simpler & more obvious. When container elements need to be erased based on a predicate, rather than iterating the container and calling unary erase, the iterator range overload is generally used with std::remove ()/std::remove_if () to minimise the number of moves of the remaining (non-removed) elements, this is the erase-remove idiom. However, I like the sound of your other solution at this point. The fact that your code seems to work is just by chance and in fact you have undefined behaviour. every iterator and reference after the point of erase is invalidated (23.3.6.5/3) Hence it (which you incremented before erase) is invalid after the erase. However, I'd rather not do it that way, if there is a way of doing the way I want. first Position of the first element removed from the vector. What do you gain from traversing the list in reverse? This code crashes, but if I use the if(it == res.end()) portion and then return, it works. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, As an aside, when writing loops like these, don't repeatedly compute the end iterator as you do here with, It seems to me that the obvious question here would be why you're doing this at all. Read our, // `erase()` invalidates the iterator, use returned iterator, // Notice that the iterator is incremented only on the else part (why? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. @Tim: I thought you wanted to avoid sending the iterator out, or walking the list twice. Example: Input: vector = {1, 4, 7, 10, 13, 16, 19}, element = 16 Output: 1 4 7 10 13 19 Input: vector = {99, 89, 79, 69, 59}, element = 89 Output: 99 79 69 59 Recommended: Please try your approach on {IDE} first, before moving on to the solution. but he should use remove_if if using an own functor iirc. It allows each element to occur only once. @Nim: doesn't this line: "foo.erase(it++);" crash it? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. reverse iterator is quite hard to use. As I said in my question, I'd rather avoid doing this, and was asking if there is any other way of doing it. It's not like this is an uncommon use-case! Number of parallelograms in a hexagon of equilateral triangles. Code will be much easier for you if you have a vector of Players not a vector of pointers to Players. Vectors are the same as dynamic arrays with the ability to resize themselves automatically when an element is inserted or deleted, with their storage being handled automatically by the container. "A random access iterator pointing to the new location of the element that followed the last element erased by the function call, which is the vector end if the operation erased the last element in the sequence.". In such case you have no invalidating of iterators, complexity is O(n), and code is very concise and you don't need to write some helper classes, although in some case using helper classes can benefit in more flexible code. How to do molecular dynamics with different isotopes of the same element? :P, I see what you mean by separating the aggregation and deletion. Erasing a specific instance of an object from a vector, Correctly erasing an element from a vector. How to get rid of black substance in render? Since calling the erase () function on the vector element invalidates the iterator, special care needs to be taken while erasing an element. This post will discuss how to remove elements from a vector while iterating inside a loop in C++. Regarding the second part of your answer, though, the update method, by its definition, can't be a const; it needs to UPDATE things, after all. Top of book ask orders are lowest ask price, and naturally sort to the beginning of the map. Is there any confirmed counterexample to causality in nature? See the last two paragraphs of my question. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. "Braces for something" - is the phrase "brace for" usually positive? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Does the policy change for AI-generated content affect users who (want to) std containers iterator invalidation during erase, Erasing data in vector via loop causing breakpoints. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Asking for help, clarification, or responding to other answers. Does this code cause undefined behavior? Why is it 'A long history' when 'history' is uncountable? How to do molecular dynamics with different isotopes of the same element? The following simplified code works, in that it deletes all vector elements. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Making statements based on opinion; back them up with references or personal experience. This code works, but please explain why next is used and how is it safe to cast a forward iterator to a reverse iterator without the world collapsing. In "Forrest Gump", why did Jenny do this thing in this scene? begin returns an iterator to the first element in the sequence container. According to the spec (c++11), this is not cool. This method returns a non-const reference so that the item at the front can be modified. Syntax: vector_name.clear () I've seen other, non-standard, containers facilatate this through "smart" iterators that know when their value has been erased (and maybe auto-jump to the next item). You repeatedly do this until there are no elements left and end() == begin(). CLang 15.0: You can use the find and consequently the erase method to remove a specific element. Data Structure & Algorithm Classes (Live), Data Structures & Algorithms in JavaScript, Data Structure & Algorithm-Self Paced(C++/JAVA), Full Stack Development with React & Node JS(Live), Android App Development with Kotlin(Live), Python Backend Development with Django(Live), DevOps Engineering - Planning to Production, GATE CS Original Papers and Official Keys, ISRO CS Original Papers and Official Keys, ISRO CS Syllabus for Scientist/Engineer Exam, Interview Preparation For Software Developers, Check if two given Circles are Orthogonal or not, Get the vector and the element to be deleted, Initialize a reverse iterator on the vector, Erase the required element with the help of base() and erase(). Why did banks give out subprime mortgages leading up to the 2007 financial crisis to begin with? res.erase(it) always returns the next valid iterator, if you erase the last element it will point to .end(). What proportion of parenting time makes someone a "primary parent"? Or course, the answers above explaining the use of reverse_iterator::base() are interesting and worth knowing, to solve the exact problem stated, I'd argue that std::remove is a better fit. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Are modes like CBC, OFB, CFB subject to chosen plaintext attacks? You could replace it with something Like "bool shouldBeErased()" and deal with erasing from the vector in the class that actually has that member, "Parent". You should take note of a bit more of the article you cited - to be portable the expression should be, I find that diagram more confusing than helpful. We are sorry that this post was not useful for you! Thanks for contributing an answer to Stack Overflow! This is generally an inefficient operation compared to the one performed for the same operation by other kinds of sequence containers (such as list or forward_list). Using pure stl you can do this in the following way (this is similar to the Motti's answer): Depending on why you are doing this, using a std::set might be a better idea than std::vector. erase-remove idiom is described in Item 32 in the book "Effective STL: 50 Specific Ways to Improve Your Use of the Standard Template Library" by Scott Meyers. The iterator first does not need to be dereferenceable if first==last: erasing an empty range is a no-op. So just used general iterator. This is the non-const version of front (), so it should allow the vector to be modified in some way. (left rear side, 2 eyelets), A film where a guy has to convince the robot shes okay. Something like this: If you cannot make update it const, just swap the element with some element from the back (you would have to keep an iterator that always points to the last element that is available for swapping). delete) you should simply call res.clear()), When you only conditionally erase elements, you probably want something like. If you can make Child::update a const method (meaning it does not modify the object, and only calls other const methods), you could write a simple functor that you can use with std::remove_if. In effect you'll defer deletion until after the first loop. Who's the alien in the Mel and Kim Christmas song? Why is it 'A long history' when 'history' is uncountable? You can accomplish this task much more efficiently using the erase-remove idiom (O(n)). Connect and share knowledge within a single location that is structured and easy to search. std::erase_if() replaces the erase-remove idiom. This would be problematic, as it is not called for every call to Child::update(), and thus that function would need a way to return an iterator to itself every single other time, and it is also currently returning another value. This is normal constructor of the reverse iterator. Funny that there is no correct solution on this page yet. If m_CursorStack is a vector, you can erase by taking index: The reason that m_map.erase((++r_iter).base() doesn't work in a loop is that erase() would invalidate the ++r_iter!! Asking for help, clarification, or responding to other answers. So if your are erasing the last element, then you try to increment the iterator that is pointing to an empty collection. Mathematica is unable to solve using methods available to solve, Closed form for a look-alike Fibonacci sequence. 2 Answers. How can I land without any propulsion? Why does removing the _first_ element of a list invalidate `.rend()`? The iterator is sometimes invalidated by the call to (*it)->update(); not most of the time, but it still occurs. Good entropy from entropy test (90B) but still fail NIST800-22. How to find and remove an object from a vector? Does Grignard reagent on reaction with PbCl2 give PbR4 and not PbR2? But erase() expects an iterator. Does the policy change for AI-generated content affect users who (want to) Erasing element from a vector rbegin() vs begin(). @FredOverflow, x can be a strucure, @Dan, and operator() a member of that structure, @ssianky Late, I know, but for completeness: No, if, How to keep your new tool from gathering dust, Chatting with Apple at WWDC: Macros in Swift and the new visionOS, We are graduating the updated button styling for vote arrows, Statement from SO: June 5, 2023 Moderator Action. C++ Vector.erase() last element corrupts iterator, Why do I get a runtime error: Vector erase iterator outside range, Expression: vector erase iterator outside range when using vector.erase(). store next item and at the end of the cycle new size of the vector. In this C++ code I try to erase element from the end of the vector but the program stops and I receive the message: Expression: vector erase iterator outside range. This is analogous to using std::remove_if, but I am not sure if it is possible/valid to use it with a predicate that modifies the objects in the sequence. Not the answer you're looking for? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. I'm unsure about the code above. You can't really iterate over and mutate a std::vector at the same time unless there's some communication between the iteration that the mutation. No need to increment, if your vector has an odd (or even, I don't know) number of elements you will miss the end of the vector. 10 Answers Sorted by: 167 res.erase (it) always returns the next valid iterator, if you erase the last element it will point to .end () At the end of the loop ++it is always called, so you increment .end () which is not allowed. Can two electrons (with different quantum numbers) exist at the same place in space? Thanks for contributing an answer to Stack Overflow! This solution is valid as std::remove_if uses the loop behind the scenes. No; all of the iterators at or after the iterator(s) passed to erase are invalidated. If it's just personal preference, that's fine. What is the problem? So you say if I understand it that I should delete the pointers and not merely the elements of the vector? That way, no elements are actually erased from the second list, and its iterators will stay valid. Your vector holds a pointer to the objects that it stores. :P. @Tim: I suspected as much, but it was not clear from your example. My code is something like this: This code obviously crashes because I am changing the end of the vector while iterating through it. Top of book bid orders are highest bid price, and naturally sort to the end of the map. EDIT: I have had a lot of answers telling me that I should separate the deletion into another loop. All operations on the reverse_iterator really occur on that underlying iterator. That's why you're getting that error. http://en.cppreference.com/w/cpp/container/vector/pop_back. A couple of other setups that I talk about in that blog post that could be relevant to these kinds of requirements are a 'vector hosted' linked list and a linked list with custom memory pool. Is there something like a central, comprehensive list of organizations that have "kicked Taiwan out" in order to appease China? detect if zone transfer with dig succeed or not via return code. Thanks for contributing an answer to Stack Overflow! It may be present multiple times and I need to clear all of them. iterator erase( const_iterator position); iterator erase( const_iterator first, const_iterator last); Parameters. alllPlayers.at(i) does not return an iterator. Well, I know that calling erase() on a vector invalidates iterators to the element and all those after it, and that erase() returns an iterator to the next valid iterator, but what if the erase happens elsewhere? Sorry about that. We can do that in many ways: 1. If the iterator pos refers to the last element, the end() iterator is returned. Connect and share knowledge within a single location that is structured and easy to search. When find something to erase. 2. Who guarantee you that iterators in a list are ordered ? Invalidates iterators and references at or after the point of the erase, including the end () iterator. What's the meaning of "topothesia" by Cicero? :P. @MaxLanghof I can't think of any other reason why it could break things. You could do this by changing the return-value of Child::update to something like std::pair, where the int is the value and the bool indicates if this element should be deleted. How is Canadian capital gains tax calculated when I trade exclusively in USD? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Does Grignard reagent on reaction with PbCl2 give PbR4 and not PbR2? How to erase reverse_iterator correctly when erase and push_back happens? A bit strange, but it works even when erasing the first or last element: If you don't need to erase everything as you go along, then to solve the problem, you can use the erase-remove idiom: std::remove swaps all the items in the container that match pCursor to the end, and returns an iterator to the first match item. 'r' It start from last element. C++ Vector.erase() last element corrupts iterator. After all is by this code the vector a vector of pointers or the way I pass them in push_back inserts only a copy of pointer? How to connect two wildly different power sources? The erase operation will also have lower time complexity than on the vector, however, adding elements is slower on the set so it might not be much of an advantage. Given a vector, the task is to erase an element from this vector using erase () and reverse_iterator. You are not allowed to use r after calling f.erase(r);. A film where a guy has to convince the robot shes okay. Which kind of celestial body killed dinosaurs? rev2023.6.12.43490. Connect and share knowledge within a single location that is structured and easy to search. I still think that deleting from the vector should not be responsibility of "Child". The element I want to remove in this particular case will nearly always be the end of the list or very close to it, so iterating in reverse is also quicker and better suited to the problem. By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. So I recommend you just do the exact same thing: return the new, valid iterator and apdapt the calling loop accordingly. Making statements based on opinion; back them up with references or personal experience. Why use your own functor when you can use equal_to? A film where a guy has to convince the robot shes okay. If God is perfect, do we live in the best of all possible worlds? Then, the erase using a range will erase from the first match, and go to the end. The same as what Space_C0wb0y said; good answer nevertheless. Why is there software that doesn't support certain platforms? You never tested that. This will just shift the same problem to the second pass. "Braces for something" - is the phrase "brace for" usually positive? Good entropy from entropy test (90B) but still fail NIST800-22. How to optimize the two tangents of a circle by passing through a point outside the circle and calculate the sine value of the angle? So it should be decreased 1 to move left. Closed form for a look-alike Fibonacci sequence. How to use efficient index seek to find the latest row filtered on a small subset of rows? Thus, the program doesn't actually "work". Your code (even if not bugged) has a memory leak. Was there any truth that the Columbia Shuttle Disaster had a contribution from wrong angle of entry? https://en.cppreference.com/mwiki/index.php?title=cpp/container/vector/erase&oldid=119433, iterators at the point of erase were not invalidated, erases all elements satisfying specific criteria. Since rbegin, ri and rend are all, Reverse iterators are liars.. when deferenced, a reverse iterator returns the element, Just to be absolutely clear, this technique still cannot be used in a normal for loop (where the iterator is incremented in the normal manner). When you erase the first element in the list, all the remaining iterators in the list become invalid. Was the Microsoft simulator right? How to erase an vector element in this situation? Calling erase will invalidate iterators, you could use: Or you could use std::remove_if together with a functor and std::vector::erase: Instead of writing your own functor in this case you could use std::remove: In C++11 you could use a lambda instead of a functor: In C++17 std::experimental::erase and std::experimental::erase_if are also available, in C++20 these are (finally) renamed to std::erase and std::erase_if (note: in Visual Studio 2019 you'll need to change your C++ language version to the latest experimental version for support): To avoid O(n^2) complexity My vector iterator is coming up with an odd error. Note that this particular method of . Maybe it is identical to. When exactly did this monstrosity happen, and where do I need to start reading to understand what happened to C++? How would I do a template (like in C++) for setting shader uniforms in Rust? Note that this particular method of removing odd elements is quite inefficient: each time you remove an element, all of the elements after it have to be moved one position to the left in the vector (this is O(n2)). Mathematica is unable to solve using methods available to solve. Erasing an element from the vector during iteration c++, using iterator to erase element in vector, C++: Using erase in a vector of iterators. OTOH, there will be more overhead for creating/incrementing/destroying iterators, so walking the list twice. EDIT: Oh, and it doesn't matter where new elements get added; what the vector says is "this is all the stuff I own". To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I.e. Weak convergence related to Hermite polynomial? Deleting an element in std::list while iterating in reverse[C++]. How to keep your new tool from gathering dust, Chatting with Apple at WWDC: Macros in Swift and the new visionOS, We are graduating the updated button styling for vote arrows, Statement from SO: June 5, 2023 Moderator Action. How hard would it have been for a small band to make and sell CDs in the early 90s? is there any way to do this without iterating through the vector multiple times or creating one more copy of the vector? size_t is an unsigned integral type (the same as member type string::size_type ). This is technically undefined behavior but if you think about what the loop is actually doing, you'll see why you get the "correct" results. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is it normal for spokes to poke through the rim this much? My understanding of how a vector would be implemented seems to suggest that the iterator is definitely usable, but I'm not entirely sure if it could lead to undefined behavior. If the vector object is const, both begin and end return a const_iterator. Similar to what Macke said, yes. See. Without that change, you could try a reverse iterator (if order did not matter), i.e. Large values will sort to the beginning of the map, and normal iterators can then be used -- eliminating the need for the reverse iterator adjustment on erase. In general, you should prefer regular iterators to reverse_iterators (as well as to const_iterators and const_reverse_iterators), for precisely reasons like this. I ran into a need to do something similar yesterday and this post was helpful. Since f.erase (r) does not capture the returned value which would be the new iterator value, and there is no other iterator incrementor, and according to documentation, erase (iterator position . It creates a new reverse iterator out of an interator. You can use this iterator to resume iteration. Does the policy change for AI-generated content affect users who (want to) c++: vector::erase called with an iterator, using iterator to erase element in vector, C++: Using erase in a vector of iterators, vector iterator not incrementable, which is related to the operation of iterator and erase, Expected number of correct answers to exam if I guess at each question. Star Trek: TOS episode involving aliens with mental powers and a tormented dwarf. acknowledge that you have read and understood our. We can obtain that iterator using the reverse_iterator::base() function. vectormap void foo() { std::vector<int> a = {1, 2, 3, 4, 5}; auto it1 = a.begin(); a.push_back(6); std::cout << *it1 << std::endl; } vectorpush_backpop_back dequelist Does the word "man" mean "a male friend"? I'm afraid I don't understand the logic of the, @SkippyleGrandGourou Thanks for the reply, I haven't really found something that matches the decrement status above. Iterator following the last removed element. But if the sequence is just a bag of values whose order we dont care about at all, then we might consider moving single elements from the end of the sequence to fill each new gap as its created: Below are their benchmark results: source: Can you find a reference to the official spec that says that? erase public member function <vector> std:: vector ::erase C++98 C++11 iterator erase (iterator position);iterator erase (iterator first, iterator last); Erase elements Removes from the vector either a single element ( position) or a range of elements ( [first,last) ). Not using pointers is the better solution as you won't have to delete anything. To complement other's answers and because I stumbled upon this question whilst searching about std::string without much success, here goes a response with the usage of std::string, std::string::erase and std::reverse_iterator. Alternatively you could use .pop_back(), but in either case, you're gonna want to deal with the memory leaks as well as mentioned in the comments. Find centralized, trusted content and collaborate around the technologies you use most. Then perhaps you can remove Parent::erase. After all is by this code the vector a vector of pointers or the way I pass them in push_back inserts only a copy of pointer? Correct algorithm: add children to delete. Return value No; all of the iterators at or after the iterator (s) passed to erase are invalidated. Weak convergence related to Hermite polynomial? Thus the end() iterator (which is valid, but is not dereferenceable) cannot be used as a value for pos. Do characters suffer fall damage in the Astral Plane? Iterators specifying a range within the string] to be removed: [first,last). Since calling the erase () function invalidates the iterator, the idea is to use its return value for setting the iterator to the next element. eg when delete 3rd element it will pointing current 4th element. Not the answer you're looking for? How can you say this works for you? At a certain point, I start to ask myself, "what am I missing?" 7 Answers Sorted by: 201 Use the remove/erase idiom: std::vector<int>& vec = myNumbers; // use shorter name vec.erase (std::remove (vec.begin (), vec.end (), number_in), vec.end ()); The method "Child::update" as somewhat strange semantics as it actually updates the parent and not the Child. Closed form for a look-alike Fibonacci sequence. What I did, then, with some similar requirements, is to stick with a vector, but to allow holes or 'dead entries' in your vector when elements are deleted. Also, pulling the floor out from beneath an iterator, Yeah, I'm not really too familiar with shared_ptr, but I think it might be better to switch to those in this case. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Asking for help, clarification, or responding to other answers. vector A fixed capacity vector. You'd need to create a copy of the iterator and do. This does not even compile. This requires the -std=c++11 flag (for auto): While using the reverse_iterator's base() method and decrementing the result works here, it's worth noting that reverse_iterators are not given the same status as regular iterators. Not the answer you're looking for? But the problem here is that the element is not guaranteed to occur only once in the vector. How do you erase *AND CONTINUE* using a std::reverse_iterator? Transformer winding voltages shouldn't add in additive polarity? Erase some of a vector's elements in a for-each loop without iterating the whole vector, Why does std::vector::insert invalidate all iterators after the insertion point, Vector gets iterated more times than size(), Vector erase will not "erase" first element, Best way to further split some elements in vector, When do Iterators in the following cases become invalidated. What was the point of this conversation between Megamind and Minion? Making statements based on opinion; back them up with references or personal experience. m_CursorStack.erase( (++i).base()) seems like it would be a problem if ++i got you to past the last element. To do so, you should start at, in the real code i am not trying to delete all the elements, but thanks, i understand what i did wrong now. Is there something like a central, comprehensive list of organizations that have "kicked Taiwan out" in order to appease China? Because of that, the memory location that used to be occupied by the deleted element, will be occupied by the next element. I think the problem is, that your method "update" also invalidates iterators in the exact same way that std::vector::erase does. But vectors tend to have a lot better performance than lists, due to much better locality of reference and also add a lot of memory overhead (in the per node prev and next pointers, but also in the form of overhead per allocated block in your system allocator). Does a drakewardens companion keep attacking the same creature or must it be told to do so every round? Not the answer you're looking for? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, What are you actually trying to do here? Who's the alien in the Mel and Kim Christmas song? Hi , I am doing in the same way , but still I am getting "out_of_range" error. erase it and return next iterator. You can use this iterator to resume iteration. The idea is to use iterators to iterate the vector and call the vector::erase function if the current element matches the predicate. Or is it neutral in this case? Are modes like CBC, OFB, CFB subject to chosen plaintext attacks? @Jan Hudec, @MSalters, and @Skurmedel: Yeah, that's how I understood it; build a separate list, perhaps another vector that holds the same pointers, and then call Parent::erase() on each of those pointers. To learn more, see our tips on writing great answers. Apparently according to the standard [24.4.1/1] the relationship between i.base() and i is: So you need to apply an offset when getting the base(). What is the problem? I will keep that in mind; thank you. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Vector iterator erase giving me a runtime error? Do characters suffer fall damage in the Astral Plane? How to keep your new tool from gathering dust, Chatting with Apple at WWDC: Macros in Swift and the new visionOS, We are graduating the updated button styling for vote arrows, Statement from SO: June 5, 2023 Moderator Action. Making statements based on opinion; back them up with references or personal experience. I think the problem is that "Child" has a dependency to "Parent". Where can one find the aluminum anode rod that replaces a magnesium anode rod? Having said that, I'd rather avoid this method, if possible. If you want to empty a vector, just use, Why the downvote? Call erase() on a duplicate of the original iterator after advancing the original iterator to the next element. Does the policy change for AI-generated content affect users who (want to) Why is my use of static vectors not working? Which containers would these be? The code runs fine on my machine, but that doesn't convince me that it's valid. Infact the relationship between itr.base() and itr is: Below is the implementation of the above approach: You will be notified via email once the article is available for improvement. I suppose I could keep the rest of this book-keeping in a separate function and call it before I call child.erase(). Does vector::erase not work with reverse iterators? What's the point of certificates in SSL/TLS? C++ vector iterator: erase() last item crash, C++ - Vector iterator + offset out of range. for example. Now that's what I like to hear. Please don't work around this by using "Ploblem" instead. EDIT: This is of course horribly broken, however it would work if you could change the container to std::list. Was there any truth that the Columbia Shuttle Disaster had a contribution from wrong angle of entry? However, erase returns a new iterator that points to the element immediately after the element (s) that were erased (or to the end if there is no such element). Find centralized, trusted content and collaborate around the technologies you use most. Are modes like CBC, OFB, CFB subject to chosen plaintext attacks? If you can communicate both erase-intent and id out of your update-function, then you can do it like this: How about adding the children to delete into a list, and delete them after you've updated every child. I will keep that in mind; thank you. How to get rid of black substance in render? Cutting wood with angle grinder at low RPM. Not the answer you're looking for? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. You want the iterator to point to the last element. Can reverse iterator be used as normal iterator? And also we cant pass a reverse iterator as a parameter to erase() function or it will give a compilation error. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. However, I do not understand why. rev2023.6.12.43490. Does the policy change for AI-generated content affect users who (want to) Iterator invalidation rules for C++ containers, Store which elements of a vector to erase, Removing an object from vector while iterating through it, c++: vector::erase called with an iterator, using iterator to erase element in vector, C++: Using erase in a vector of iterators, Erasing an element of a vector that uses const_iterator, using std::vector::erase with const_iterators. Why have God chosen to order offering Isaak as a whole-burnt offering to test Abraham? Does not throw unless an exception is thrown by the assignment operator of T. Linear: the number of calls to the destructor of T is the same as the number of elements erased, the assignment operator of T is called the number of times equal to the number of elements in the vector after the erased elements, // Erase all even numbers (C++11 and later). Thanks everyone. FWIW, Qt has a "deleteLater()" on their objects, showing that a common way to address this issue is to defer the deletion out of the update. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The order of the non-matching elements is preserved. Which kind of celestial body killed dinosaurs? :-P, i thinkhe does exactly that. From the looks of it, though, I suck at coding and will have to rewrite. To learn more, see our tips on writing great answers. Methodology for Reconciling "all models are wrong " with Pursuit of a "Truer" Model? How to properly center equation labels in itemize environment? Inside the loop, curr will never be equal to res.end(), and it will be at the next element regardless of if you erase it from your vector. I have the following situation (simplified): WARNING: Do NOT assume that this is the entire code. Yes, either that, or don't use pointers. And here is the piece of code to convert the result of erase back to a reverse iterator in order to erase an element in a container while iterating in the reverse. Difference between std::remove and vector::erase for vectors, Initializing Vector using an Existing Vector in C++ STL, Erase Range of Elements From List Using Iterators in C++ STL, vector::front() and vector::back() in C++ STL, vector::empty() and vector::size() in C++ STL, vector::push_back() and vector::pop_back() in C++ STL, vector::operator= and vector::operator[ ] in C++ STL, vector::at() and vector::swap() in C++ STL, vector::begin() and vector::end() in C++ STL, A-143, 9th Floor, Sovereign Corporate Tower, Sector-136, Noida, Uttar Pradesh - 201305, We use cookies to ensure you have the best browsing experience on our website. Use a regular iterator to iterate backwards, or struggle with reverse_iterator? How to remove from a map while iterating it? Do not erase and then increment the iterator. Capturing number of varying length at the beginning of each line with sed. c++vector // 0 4vectornumbers std::vector<int> numbers {0, 1, 2, 3, 4}; // ab int a = 1; int b = 3; // iterator for (auto itr = numbers.begin (); itr != numbers.end (); itr++) { if ( ( (*itr) == a) || ( (*itr) == b)) { numbers.erase (itr); } } :P Well, I was hoping for a "cool" alternative, but I guess I'll have to go with either the deleteme or second loop method. How to do molecular dynamics with different isotopes of the same element? By clicking Post Your Answer, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct. Why does Tony Stark always call Captain America by his last name? Why does Tony Stark always call Captain America by his last name? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why did banks give out subprime mortgages leading up to the 2007 financial crisis to begin with? When you aggregation is done, just discard the end of the vector (that now contains all the elements that are to be deleted) using vector::resize. How can i use iterator with vector erase? Thus the end() iterator (which is valid, but is not dereferencable) cannot be used as a value for pos. What bread dough is quick to prepare and requires no kneading or much skill? Why std::vector iterator is invalidated after the erase() call? for exmaple via return value, setting a member, and so on. There are 3 main problems that I see. std::vector<int> numbers; numbers.push_back (2); numbers.front () += 10; Does the ratio of C in the atmosphere show that global warming is not due to fossil fuels? Can you please tell me why ? Asking for help, clarification, or responding to other answers. Transformer winding voltages shouldn't add in additive polarity? Is it normal for spokes to poke through the rim this much? Adding/removing elements to/from vector in most cases (that includes erase())invalidates references and iterators. How to call erase with a reverse iterator, How to keep your new tool from gathering dust, Chatting with Apple at WWDC: Macros in Swift and the new visionOS, We are graduating the updated button styling for vote arrows, Statement from SO: June 5, 2023 Moderator Action. How do I pass a "const_reverse_iterator" parameter to "std::vector::erase()"? Purpose of some "mounting points" on a suspension fork? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Something that you can do with modern C++ is using "std::remove_if" and lambda expression; The it++ instruction is done at the end of the block. Think of it as the Child declaring independence from the Parent, and thus no longer being "owned" by the Parent. So, the following is the correct one: In case of the forward iterator the solution is straight forward: In case of reverse iterator you need to do the same: Please note that m_CursorStack.erase( (++i).base()) may be a problem if used in a for loop (see original question) because it changes the value of i. vector<int> v = { 1, 5, 10, 15, 20 }; for (auto it = v.begin (); it != v.end (); it++) if ( (*it) == 5) v.push_back (-1); for (auto it = v.begin (); it != v.end (); it++) cout << (*it) << " "; return 0; } Output 1 5 10 15 20 -1 -1

Inspection Certification, Carthage Ruins Tunisia, Crispy Cornflake Cookies, Debbie Crosbie Nationwide Salary, Fragilely Pronunciation, Memorial Hermann Labor And Delivery Cost,