In his book The C++ Standard Library (Second Edition) Nicolai Josuttis states that lambdas can be better optimized by the compiler than plain functions. In addition, C++ compilers optimize lambdas better than they do ordinary functions. (Page 213) Why is that? I thought when it comes to inlining there shouldn’t be any difference any more. … Read more
Once it is compiled, is there a difference between: delegate { x = 0; } and () => { x = 0 } ? 6 Answers 6
How do I capture by move (also known as rvalue reference) in a C++11 lambda? I am trying to write something like this: std::unique_ptr<int> myPointer(new int); std::function<void(void)> example = [std::move(myPointer)]{ *myPointer = 4; }; 6 Answers 6
In Java, is it possible to have a lambda accept multiple different types? I.e: Single variable works: Function <Integer, Integer> adder = i -> i + 1; System.out.println (adder.apply (10)); Varargs also work: Function <Integer [], Integer> multiAdder = ints -> { int sum = 0; for (Integer i : ints) { sum += i; … Read more
This is a simplified version of the original problem. I have a class called Person: public class Person { public string Name { get; set; } public int Age { get; set; } public int Weight { get; set; } public DateTime FavouriteDay { get; set; } } …and lets say an instance: var bob … Read more
I am new to C++11. I am writing the following recursive lambda function, but it doesn’t compile. sum.cpp #include <iostream> #include <functional> auto term = [](int a)->int { return a*a; }; auto next = [](int a)->int { return ++a; }; auto sum = [term,next,&sum](int a, int b)mutable ->int { if(a>b) return 0; else return term(a) … Read more
I don’t quite understand the syntax behind the sorted() argument: key=lambda variable: variable[0] Isn’t lambda arbitrary? Why is variable stated twice in what looks like a dict? 10 Answers 10
Why can’t you use a ref or out parameter in a lambda expression? I came across the error today and found a workaround but I was still curious why this is a compile-time error. CS1628: Cannot use in ref or out parameter ‘parameter’ inside an anonymous method, lambda expression, or query expression Here’s a simple … Read more
I have a problem trying out the Lambda expressions of Java 8. Usually it works fine, but now I have methods that throw IOException‘s. It’s best if you look at the following code: class Bank{ …. public Set<String> getActiveAccountNumbers() throws IOException { Stream<Account> s = accounts.values().stream(); s = s.filter(a -> a.isActive()); Stream<String> ss = s.map(a … Read more
There is a lot of talk about monads these days. I have read a few articles / blog posts, but I can’t go far enough with their examples to fully grasp the concept. The reason is that monads are a functional language concept, and thus the examples are in languages I haven’t worked with (since … Read more
