predicate

问题 I have a list of nodes, where each of the nodes belong to one or multiple trees. (they do not necessarily share a common ancestor) I want to sort the nodes in the same order I would find them when doing a Depth First Search. Let say I have a predicate for sorting tree roots together, and another predicate to sort children of a common parent together. Each node have a Parent accessor, and a children enumerator. I want to avoid using the Children enumeration for performance reasons (if possible

问题 All Objects from core data { dtStartDate = "Jun 10, 2016-10:40 AM"; }, { dtStartDate = "May 12, 2016-06:55 AM"; }, { dtStartDate = "May 12, 2016-08:05 AM"; }, { dtStartDate = "May 12, 2016-02:30 PM"; }, { dtStartDate = "Jun 12, 2016-07:50 AM"; }, { dtStartDate = "Jul 12, 2016-08:50 AM"; }, { dtStartDate = "Jun 12, 2016-07:50 AM"; }, { dtStartDate = "May 12, 2016-10:00 AM"; }, { dtStartDate = "Jun 12, 2016-07:30 AM"; } I use this date format to predicate core data NSDate *dt = [NSDate date];

问题 I have a many-to-many relationship between two entities; Item and Tag. I'm trying to create a predicate to take the selectedItem and return a ranking of items based on how many similar tags they have. So far I've tried: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SUBQUERY(itemToTag, $item, $item in %@).@count > 0", selectedItem.itemToTag]; Any other iterations that have failed. It currently only returns the selectedItem in the list. I've found little on Subquery. Is there a

问题 I have a simple TableViewController which has an add button which goes over to a ModalViewController; the user adds in text into a text field, presses save and that dismisses and the entry is added to the Entities and Attributes in Core Data and displayed in the TableViewController. It works well. I firstly started off with another button that pulled up a UISearchBar in a Table View and I could search for results and pull that back; that worked. I then added a new tab to the bottom of the

问题 I am trying to pass in a string value ("GreaterThan", "Equals", etc.) for a numeric operand expression to a parameter. I have created the code below which works, but it's "clunky". I don't like the if blocks and I think there's a way to do this with a custom LINQ comparison predicate. I tried to follow the reply posted in this post , but I can't seem to follow it. Any ideas on how to clean up my method? Here's code showing how I want to pass a string value of "GreaterThan" to a function var

问题 How would you transform the following prolog statement to predicate logic? hates(amy, X). 回答1: Using LaTeX's \forall to denote the universal quantifier, the meaning of hates(amy,x). is: \forall x hates(amy,x) In general, Prolog variables that occur in a program are universally quantified and Prolog variables that occur in a query are existentially quantified. For instance ?- hates(amy,x). would be represented by \exists x hates(amy,x) in FOL. 来源： https://stackoverflow.com/questions/25840140

问题 How can I replace a value if it fails a predicate? To illustrate: assert_eq!((3-5).but_if(|v| v < 0).then(0), 0) I thought there would be something on Option or Result to allow this, but I cannot find it. 回答1: I thought there would be something on Option or Result But neither of these types appear here. Subtracting two numbers yields another number. It appears you just want a traditional if-else statement: fn main() { let a = 3 - 5; assert_eq!(if a < 0 { 0 } else { a }, 0); } Since you have

问题 Each restaurant can have multiple managers. class Restaurant(models.Model): ... managers = models.ManyToManyField(User, related_name='restaurants_which_they_manage') Only restaurant managers can change a restaurant listing. I'm using django-rules to enforce this. I've got a predicate that creates a nice verbose "is_restaurant_manager" reference : @rules.predicate def is_restaurant_manager(user, restaurant): return user in restaurant.managers.all() And here is the permission : rules.add_perm(

问题 I have an Array of MKAnnotation objects called arrAnnotations . I want to pick out one of the annotations with the same coordinate as the one stored in a CLLocation object called "newLocation". I'm trying to use a NSPredicate , but it doesn't work. NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(SELF.coordinate == %f)", newLocation.coordinate]; NSArray* filteredArray = [arrAnnotations filteredArrayUsingPredicate:predicate]; [self.mapView selectAnnotation:[filteredArray

问题 I have intialized Hash map inside static block, I need to access the hashmap object to get the value using key it inside my getExpo method. My class goes here public class ExampleFactory { static { HashMap<String,Class<?>> hmap = new HashMap<String,Class<?>>(); hmap.put("app", application.class); hmap.put("expo", expession.class); } public void getExpo(String key,String expression) { // I need to access the object in static block Class aclass=hmap.get(key); // it works when i place it inside