iterator

问题 I am trying to turn a Map("a" -> 2, "b" -> 1) into seq("a","a","b") through the map function, Currently I am trying to run the code below giving me the desired result. Is there a smarter way to do this? Possibly a better way through the map function? var multiset : Seq[T] = Seq[T]() var variables : Seq[T] = data.map(x => x._1).toSeq var variableCounts : Seq[Int] = data.map(x => x._2).toSeq for(x <- 0 until variables.length){ for(y <- 0 until variableCounts(x)) multiset = multiset :+ variables

问题 I am trying to turn a Map("a" -> 2, "b" -> 1) into seq("a","a","b") through the map function, Currently I am trying to run the code below giving me the desired result. Is there a smarter way to do this? Possibly a better way through the map function? var multiset : Seq[T] = Seq[T]() var variables : Seq[T] = data.map(x => x._1).toSeq var variableCounts : Seq[Int] = data.map(x => x._2).toSeq for(x <- 0 until variables.length){ for(y <- 0 until variableCounts(x)) multiset = multiset :+ variables

问题 I am trying to turn a Map("a" -> 2, "b" -> 1) into seq("a","a","b") through the map function, Currently I am trying to run the code below giving me the desired result. Is there a smarter way to do this? Possibly a better way through the map function? var multiset : Seq[T] = Seq[T]() var variables : Seq[T] = data.map(x => x._1).toSeq var variableCounts : Seq[Int] = data.map(x => x._2).toSeq for(x <- 0 until variables.length){ for(y <- 0 until variableCounts(x)) multiset = multiset :+ variables

问题 Variadic Zip Function Swift 4.1, Xcode 9.4 I have been using Apple's native zip(_:_:) recently and I ran into a situation whereby I needed to zip more than two sequences. So I looked for and found the declaration of zip(_:_:) on Swift's GitHub page. I took that information and was able to overload zip(_:_:) to accept four parameters, zip(_:_:_:_:) . I am aware that I can painstakingly overload zip to support whatever number of arguments I chose one at a time, but this is inflexible, time

问题 I would like to iterate over a vector several times: let my_vector = vec![1, 2, 3, 4, 5]; let mut out_vector = vec![]; for i in my_vector { for j in my_vector { out_vector.push(i * j + i + j); } } The j-loop has a "value used here after move" error. I know that I can place an & before the two my_vector s and borrow the vectors, but it is nice to have more than one way to do things. I would like a little insight as well. Alternatively, I can write the following: let i_vec = vec![1, 2, 3, 4, 5,

问题 I would like to iterate over a vector several times: let my_vector = vec![1, 2, 3, 4, 5]; let mut out_vector = vec![]; for i in my_vector { for j in my_vector { out_vector.push(i * j + i + j); } } The j-loop has a "value used here after move" error. I know that I can place an & before the two my_vector s and borrow the vectors, but it is nice to have more than one way to do things. I would like a little insight as well. Alternatively, I can write the following: let i_vec = vec![1, 2, 3, 4, 5,

问题 The Dart core API has two classes that implement the Queue<E> interface, DoubleLinkedQueue<E> and ListQueue<E>. The documentation of both classes is almost identical, the only difference that is explicitly mentioned is the following note in the ListQueue<E> documentation: Operations like removeAll and removeWhere are very inefficient. If those are needed, use a DoubleLinkedQueue instead. What is the actual difference between them implementation-wise and when should which implementation be

问题 The Dart core API has two classes that implement the Queue<E> interface, DoubleLinkedQueue<E> and ListQueue<E>. The documentation of both classes is almost identical, the only difference that is explicitly mentioned is the following note in the ListQueue<E> documentation: Operations like removeAll and removeWhere are very inefficient. If those are needed, use a DoubleLinkedQueue instead. What is the actual difference between them implementation-wise and when should which implementation be

问题 The Dart core API has two classes that implement the Queue<E> interface, DoubleLinkedQueue<E> and ListQueue<E>. The documentation of both classes is almost identical, the only difference that is explicitly mentioned is the following note in the ListQueue<E> documentation: Operations like removeAll and removeWhere are very inefficient. If those are needed, use a DoubleLinkedQueue instead. What is the actual difference between them implementation-wise and when should which implementation be

问题 This question already has answers here : Java - Iterating over every two elements in a list (11 answers) Closed 4 years ago . I have an ArrayList and I want to iterate over it each 2 elements, like this: ([1,2], [3, 4], [5, 6]) Currently I'm able to iterate the list like this: ([1,2], [2, 3], [3, 4]) but this is not the result I want. Here is my code: Iterator<MyObject> iterator = myList.iterator(); if (iterator.hasNext()) { MyObject o1 = iterator.next(); while (iterator.hasNext()) { final