remove-if

问题 I want to remove elements (histogram bins) from an std::unordered_map (histogram) that fulfills a predictate (histogram bins having zero count) given as a lambda expression as follows std::remove_if(begin(m_map), end(m_map), [](const Bin & bin) { return bin.second == 0; }); but GCC-4.6.1 complains as follows /usr/include/c++/4.6/bits/stl_pair.h:156:2: error: assignment of read-only member ‘std::pair<const unsigned char, unsigned char>::first’ /usr/include/c++/4.6/bits/stl_pair.h: In member

问题 I want to remove elements (histogram bins) from an std::unordered_map (histogram) that fulfills a predictate (histogram bins having zero count) given as a lambda expression as follows std::remove_if(begin(m_map), end(m_map), [](const Bin & bin) { return bin.second == 0; }); but GCC-4.6.1 complains as follows /usr/include/c++/4.6/bits/stl_pair.h:156:2: error: assignment of read-only member ‘std::pair<const unsigned char, unsigned char>::first’ /usr/include/c++/4.6/bits/stl_pair.h: In member

问题 Is there any method where i can create a json from a spark dataframe by not using those fields which are null: Lets suppose i have a data frame: +-------+----------------+ | name| hit_songs| +-------+----------------+ |beatles|[help, hey jude]| | romeo| [eres mia]| | juliet| null | +-------+----------------+ i want to convert it into a json like: [{ name: "beatles", hit_songs: [help, hey jude] }, { name: "romeo", hit_songs: [eres mia] }, { name: "juliet" } ] i dont want the field hit_songs in

问题 Is there any method where i can create a json from a spark dataframe by not using those fields which are null: Lets suppose i have a data frame: +-------+----------------+ | name| hit_songs| +-------+----------------+ |beatles|[help, hey jude]| | romeo| [eres mia]| | juliet| null | +-------+----------------+ i want to convert it into a json like: [{ name: "beatles", hit_songs: [help, hey jude] }, { name: "romeo", hit_songs: [eres mia] }, { name: "juliet" } ] i dont want the field hit_songs in

问题 I have a list e.g. l1 = [1,2,3,4] and another list: l2 = [1,2,3,4,5,6,7,1,2,3,4] . I would like to check if l1 is a subset in l2 and if it is, then I want to delete these elements from l2 such that l2 would become [5,6,7,1,2,3,4] , where indexes 0-3 have been removed. Is there a pythonic way of doing this? I tried this: l1 = [1,2,3,4] l2 = [1,2,3,4,5,6,7,1,2,3,4] l3 = [] for i in l2: if i in l1: l3.append(i) -> prints [5,6,7] However I would like the output to be [5,6,7,1,2,3,4] . 回答1: Well,

问题 I have this: Post.paragraphs << new_paragraph And I need to remove paragraph by id = 3, so the following deletes the record completely: Post.paragraphs.find(paragraph_id).destroy # or Post.paragraphs.find(paragraph_id).delete I just need to remove a paragraph from has_many association. I tried to use delete and destroy . Both methods completely delete records from the associated tables. How can I just remove them from the "container"? 回答1: You should not use the delete method on the Paragraph

问题 This question already has answers here : Erasing elements from a vector (5 answers) Closed 5 years ago . Here my code. I want remove from vector all elements with successfully called method 'release'. bool foo::release() { return true; } // ... vector<foo> vec; // ... remove_if(vec.begin(), vec.end(), [](foo & f) { return f.release() == true; }); // ... But remove_if not deleting all elements from vector vec . How remove_if works? 回答1: std::remove_if re-arranges the elements of the vector

问题 Given std::vector<double> a; std::vector<int> ind; where ind is 1 sorted in ascending order. I want to do the equivalent of the following: for (auto it=ind.rbegin();it!=ind.rend();it++) a.erase(a.begin() + *it); I came up with this: for (auto it=ind.begin();it!=ind.end();it++) a[*it] = std::numeric_limits<double>::max(); std::erase(std::remove(a.begin(),a.end(),std::numeric_limits<double>::max()),a.end()); This is very fast, but it doesn't feel right to use the std::numeric_limits::max() as a

问题 This question already has answers here : pair-wise duplicate removal from dataframe [duplicate] (4 answers) Closed 3 years ago . The data I have is something like that: RES1 <- c("A","B","A","A","B") RES2 <- c("B","A","A","B","A") VAL1 <-c(3,5,3,6,8) VAL2 <- c(5,3,7,2,7) dff <- data.frame(RES1,VAL1,RES2,VAL2) dff RES1 VAL1 RES2 VAL2 1 A 3 B 5 2 B 5 A 3 3 A 3 A 7 4 A 6 B 2 5 B 8 A 7 I want to remove the lines where I already have the same res1-res2 pair. For example: A 3 interacts with B 5.

问题 I have a std::list of classes and want to remove entries that are marked for delete. I am using std::remove_if and erase. class MyClass { bool isDone(MyData& myData) { return myData.isDone(); } void removeIfDone(std::list<MyData>& myList) { std::list<MyData>::iterator it = remove_if(myList.begin(), myList.end(), boost::bind(&MyClass::isDone, this, _1)); myList.erase(it, myList.end()); } }; I am running on a small processor for which memory allocation and deallocation is very expensive. This