Could someone explain? I understand the basic concepts behind them but I often see them used interchangeably and I get confused. And now that we’re here, how do they differ from a regular function? 15 s 15 There is a lot of confusion around lambdas and closures, even in the answers to this StackOverflow question … Read more
Closed. This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 6 years ago. Improve this question I’m trying to figure out Python lambdas. Is lambda one of those “interesting” language items … Read more
I have a list that I want to filter by an attribute of the items. Which of the following is preferred (readability, performance, other reasons)? xs = [x for x in xs if x.attribute == value] xs = filter(lambda x: x.attribute == value, xs) 15 s 15 It is strange how much beauty varies for … Read more
I want to translate a List of objects into a Map using Java 8’s streams and lambdas. This is how I would write it in Java 7 and below. private Map<String, Choice> nameMap(List<Choice> choices) { final Map<String, Choice> hashMap = new HashMap<>(); for (final Choice choice : choices) { hashMap.put(choice.getName(), choice); } return hashMap; } … Read more
I understand lambdas and the Func and Action delegates. But expressions stump me. In what circumstances would you use an Expression<Func<T>> rather than a plain old Func<T>? 1Best Answer 11 When you want to treat lambda expressions as expression trees and look inside them instead of executing them. For example, LINQ to SQL gets the … Read more
What is a lambda expression in C++11? When would I use one? What class of problem do they solve that wasn’t possible prior to their introduction? A few examples, and use cases would be useful. 10 The problem C++ includes useful generic functions like std::for_each and std::transform, which can be very handy. Unfortunately they can … Read more
When using lambda expressions or anonymous methods in C#, we have to be wary of the access to modified closure pitfall. For example: foreach (var s in strings) { query = query.Where(i => i.Prop == s); // access to modified closure … } Due to the modified closure, the above code will cause all of … Read more
You can just copy the value of readln2 into a final variable: final String labelText = readln2 ; Button button = new Button(“Click the Button”); button.setOnAction(e -> l.setText(labelText)); If you want to grab a new random line each time, you can either cache the lines of interest and select a random one in the event handler: Button button = … Read more
A final variable means that it can be instantiated only one time. in Java you can’t reassign non-final local variables in lambda as well as in anonymous inner classes. You can refactor your code with the old for-each loop: private TimeZone extractCalendarTimeZoneComponent(Calendar cal,TimeZone calTz) { try { for(Component component : cal.getComponents().getComponents(“VTIMEZONE”)) { VTimeZone v = … Read more
