map

问题 For this nested map called "tables", (def tables {:tableA {:occupied false :party nil} :tableB {:occupied true :party nil} :tableC {:occupied false :party nil}}) how do I filter and get back the keys where :occupied = false ? correct result should be (:tableA :tableC) can I do this with "filter" HOF? Should I be using a list comprehension? 回答1: You could do it pretty easily with keep : (keep (fn [[k v]] (if-not (:occupied v) k)) tables) However, as you observed, using for is often a good

问题 I want to show a route between my current location and desired location. I am able to do this but when the source point and destination point so far then it will not show a route and gave the memory warning. Can you suggest any sample code or any way to do this? 回答1: Following Code for the draw path between the current location to desire location - (void)viewDidLoad { [super viewDidLoad]; mapView = [[[MapView alloc] initWithFrame: CGRectMake(0, 0, self.view.frame.size.width, self.view.frame

问题 I need to have a HashMap< Integer, String> which can serve fast operations for retrieving a list of all entries whose keys are in a certain integer range besides, getting values from map based on keys. What Map implementation is suitable for these needs ? 回答1: Use a TreeMap , which implements NavigableMap supplying a subMap method returning a view of the map with only keys in your range. To get the values, of course you call values() on the result. If you have an existing Map whose keys

问题 Is it possible in vim to do a conditional map, in normal mode? I've seen it for insert mode. I want to remap gq, depending on the outcome of a function. Something like: nnoremap gq if(g:set_formatprg()) | gq | else | = | endif Notice that g:set_formatprg() will not always have the same value, so it cannot be replaced by if(!g:set_formatprg()) | nnoremap gq = | endif 回答1: An expression map makes it easy nnoremap <expr> gq g:set_formatprg() ? 'gq' : '=' For more help see :h map-expression 来源：

问题 Following the pointers in an ebay tech blog and a datastax developers blog, I model some event log data in Cassandra 1.2. As a partition key, I use “ddmmyyhh|bucket”, where bucket is any number between 0 and the number of nodes in the cluster. The Data model cqlsh:Log> CREATE TABLE transactions (yymmddhh varchar, bucket int, rId int, created timeuuid, data map, PRIMARY KEY((yymmddhh, bucket), created) ); (rId identifies the resource that fired the event.) (map is are key value pairs derived

问题 I need a structure for my little Python program to save a list of max 500 names with one number each. The names would be unique, but the numbers would repeat (often). I first thought of a dictionary, but I also need to be able to search for the numbers, for instance I would need to change all 2 to 3 . What would you recommend? I am new to Python, so I am sure I overlooked a simple solution. ("Spiderman",1) ("Dr. House",2) ("Jon Skeet",1) 回答1: You can use a dict, and search by value like so:

问题 I am creating an evaluator for scheme in scheme, and one of the features I want it to have is map. However, all the definitions for map I've found do not allow for multiple lists. For example: (define (my-map proc lis) (cond ((null? lis) '()) ((pair? lis) (cons (proc (car lis)) (my-map proc (cdr lis)))))) This definition of map is 'incomplete' because, for example, you cannot add 2 lists of numbers with it like so (it only allows one list as an argument): (my-map + '(1 2 3) '(4 5 6)) How do I

问题 OK I start with a blank map, which is 512x512 = 262144 pixels/locations. I need a way to efficiently draw some objects on it, and then be able to find the areas of free space, so that later more different objects can be added to these free areas. I cant figure out the best way to store this data, or algorithms to find the free areas. I had a working solution, but it took forever to compute. I'm working with AS3, in case that impacts what would be the best solution. Any Advice? thanks. 回答1:

问题 Is there any way to obtain a depth map in three.js? I am interested in producing something similar to what a Kinect would produce for a given scene. I have come across a hacky way of using no colors and fog to mimic this but it would not be ideal because it would use two different scenes and would be variant to lighting. Another way to do this I believe would be to access the depth buffer but it appears this cannot be accessed through three.js. 回答1: Yep. Try using MeshDepthMaterial . 来源：

问题 I want my map to be searchable and I want to be capable to kick out from it elements that were inserted into it longest time ago (with api like map.remove(map.get_iterator_to_oldest_inserted_element()) ) like mix of queqe and map.. Is there any such container in STL or Boost? 回答1: You can use boost::multi_index using the ordered_unique and sequence indices, as in this example. #include <iostream> #include <boost/multi_index_container.hpp> #include <boost/multi_index/ordered_index.hpp>