predicate

问题 Pointers in C++ may in general only be compared for equality. By contrast, less-than comparison is only allowed for two pointers that point to subobjects of the same complete object (e.g. array elements). So given T * p, * q , it is illegal in general to evaluate p < q . The standard library contains functor class templates std::less<T> etc. which wrap the built-in operator < . However, the standard has this to say about pointer types (20.8.5/8): For templates greater , less , greater_equal ,

问题 I want to create an object with a constructor containing predicate and func objects in the xml config using spring. The Predicate and the Func arguments should point to a method of another configured object. How is this possible using Spring.net? I was not able to find a solution or hint in the documentation... A sample constructor would be: MyClass(Predicate<TInput> condition, Func<TInput, TOutput> result) 回答1: It is also possible to use the DelegateFactoryObject within Spring.net to create

问题 Consider the arrays below. The arrays contain objects of type 'Alpha'. We only care about the property username which is of type NSString . NSArray *some_usernames = @[ <multiple values of type Alpha> ] NSArray *all_usernames = @[ <multiple values of type Alpha> ] I basically want a list of all the usernames that are not in the array some_usernames , i.e. NSArray *remaining_usernames = @[ <all_usernames but not in some_usernames> ]; The way I would intend to do is: NSPredicates *predicates;

问题 Consider the arrays below. The arrays contain objects of type 'Alpha'. We only care about the property username which is of type NSString . NSArray *some_usernames = @[ <multiple values of type Alpha> ] NSArray *all_usernames = @[ <multiple values of type Alpha> ] I basically want a list of all the usernames that are not in the array some_usernames , i.e. NSArray *remaining_usernames = @[ <all_usernames but not in some_usernames> ]; The way I would intend to do is: NSPredicates *predicates;

问题 I am trying to build a complex xpath expression which will answer the following condition. From the XML data below, returns the User entity which: His loginname is " user1 " His name is " User 1 " He has 2 different profiles values which are " operator " and " admin " (I don't know the exact order ahead) <user> <login>user1</login> <name>User 1</name> <profile> <value>admin</value> <id>2</id> <description>admin users</description> </profile> <profile> <value>operator</value> <id>1</id>

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 8 years ago . Can you give some example or a link to a topic. 回答1: A predicate is a C++ function returning a boolean or an object having a bool operator() member. A unary predicate takes one argument, a binary takes two, and

问题 I'm using LINQ to Entities for Entity Framework objects in my Data Access Layer. My goal is to filter as much as I can from the database, without applying filtering logic to in-memory results. For that purpose Business Logic Layer passes a predicate to Data Access Layer. I mean Func<MyEntity, bool> So, if I use this predicate directly, like public IQueryable<MyEntity> GetAllMatchedEntities(Func<MyEntity, Boolean> isMatched) { return qry = _Context.MyEntities.Where(x => isMatched(x)); } I'm

问题 Google Guava has a predicate that always returns true. Does Java 8 have something similar for its Predicate ? I know I could use (foo)->{return true;} , but I want something pre-made, analogous to Collections.emptySet() . 回答1: There are no built-in always-true and always-false predicates in Java 8. The most concise way to write these is x -> true and x -> false Compare these to Predicates.alwaysTrue() // Guava and finally to an anonymous inner class: new Predicate<Object>() { public boolean

问题 I have an attribute of type BOOL and I want to perform a search for all managed objects where this attribute is YES . For string attributes it is straightforward. I create a predicate like this: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"userName = %@", userName]; But how do I do this, if I have a bool attribute called selected and I want to make a predicate for this? Could I just do something like this? NSPredicate *predicate = [NSPredicate predicateWithFormat:@"selected = %

问题 Quick question: Which one is faster? foreach (Object obj in Collection) { if(obj.Mandatory){ ... } } or foreach (Object obj in Collection.FindAll(o => o.Mandatory)) { ... } and if you know a faster suggestion, i'd be pleased to know. Thank you 回答1: The following test code prints the system ticks (1 tick = 100 nanoseconds) for iterating through 10 million objects. The FindAll is slowest and the for loop is fastest as expected. But the overhead of the iteration is measured in nanoseconds per