lambda

问题 I am trying to call the following Kotlin function from Java override fun First(list: LinqList<ElementType>, condition: (ElementType) -> Boolean) : ElementType like this int first = list.First(list,(x) -> x == 5); but i get the following error Error java: cannot access kotlin.jvm.functions.Function1 class file for kotlin.jvm.functions.Function1 not found I have tried googling it but i can not find the answer anywhere Thanks in advance 回答1: My problem got fixed when I configured Kotlin compiler

问题 I'm using java 8 and lambda expressions. When I use lambda expressions with OnClickListeners everything is fine, but when I use that in this animate method: public void configureFragmentToolbar(String title, boolean displayHomeAsUpEnabled) { //.. this.toolbar.animate().translationY(-50).setDuration(300).withEndAction(() -> { //ERROR toolbar.animate().translationY(0).setDuration(300); }); } I´m getting this error: "error: cannot find symbol method metafactory(Lookup,String,MethodType

问题 Trying to override map::compare function using lambda, it seems that the following solution works. auto cmp = [](const int&a, const int& b) { return a < b; }; std::map<int, int, decltype(cmp)> myMap(cmp); But, I had to define cmp first and use it later. Can I do this without defining 'cmp'? 回答1: No, you can't use lambda in unevaluated context -- i.e. template parameters as in your example. So you must define it somewhere else (using auto ) and then use decltype ... the other way, as it was

问题 What is the best way in C++11 (ie. using C++11 techniques) to validate cin input? I've read lots of other answers (all involving cin.ignore, cin.clear, etc.), but those methods seem clumsy and result in lots of duplicated code. Edit: By 'validation', I mean that both well-formed input was provided, and that it satisfies some context-specific predicate. 回答1: I'm posting my attempt at a solution as an answer in the hopes that it is useful to somebody else. It is not necessary to specify a

问题 Is it possible to define the contents of a lambda expression (delegate, Action, Func<>) with Razor syntax, so that when this model method is executed in the view, it will insert that Razor content? The intended purpose of this is for our developers to be able to define their own custom content to be inserted at a particular point in the CustomControl's view. The following is stripped-down example code that mimics my current layout. The particular parts of focus are the RenderSideContent

问题 I am trying to test some code inside lambda expression which is a call back from another class. class EmailSender { private EmailBuilder emailBuilder; public void send() { String testEmail = emailBuilder.buildEmail("Test Email", bodyContentAppender()); //send testEmail } private Consumer<Email> bodyContentAppender() { //how to test this through JUnit? return email -> email.appendBody("Body Content"); } } interface EmailBuilder { String buildEmail(String templateName, Consumer<Email>

问题 I get an exception when I call metafactory . It says: java.lang.invoke.LambdaConversionException: Incorrect number of parameters for instance method invokeVirtual my.ExecuteTest$AProcess.step_1:()Boolean; 0 captured parameters, 0 functional interface method parameters, 0 implementation parameters I do not understand all from the documentation of LambdaMetafactory.metafactory . I have problems figuring out the correct parameters: MethodHandles.Lookup caller -- thats easy String invokedName --

问题 I have several Lambda Functions that are on a schedule and those are working without any issues. However, I have a onetime job that I am trying to set up for an existing function and am getting an error when I am creating the new rule: Details: Parameter ScheduleExpression is not valid.. I need this to run on Monday September 26th 2016 at 14:30 hours UTC. Here are all of the variations I have tried: cron(30 14 26 SEP ? 2016) cron(30 14 26 9 ? 2016) cron(30 14 26 SEP ?*) cron(30 14 26 9 ? *)

问题 when I run this code Expression left = Expression.Constant(10, typeof(int)); Expression right = Expression.Constant(10,typeof(int)); var method10 = typeof(Expression).GetMethod("Equal", new[] { typeof(Expression), typeof(Expression) }); Expression exp = Expression.Call(method10,left,right); var lambda = Expression.Lambda<Func<bool>>(exp); var compiled = lambda.Compile().DynamicInvoke(); I get the below error Additional information: Expression of type 'System.Int32' cannot be used for

问题 I am needing to sort a list that contains tuples inside. I can sort them using key=lambda . The list is larger than 1000 elements. >>> a = [(<object>, 4), (<object>, 5), (<object>, -2)....] >>> b = sorted(a, key=lambda tup: tup[1]) Is there a faster way to accomplish this? 回答1: You can use itemgetter >>> from operator import itemgetter >>> a = [(None, 4), (None, 5), (None, -2)] >>> b = sorted(a, key=itemgetter(1)) >>> b [(None, -2), (None, 4), (None, 5)] Now if you want to look at the