lambda Questions

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A requires-expression similarly to a function can introduce local parameters using a parameter list. And lambda expressions defined at block scope may have captures without initializers. Is it allo...
Interlace asked 25/9 at 19:40

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I've converted some code from vb.net to c# but it's having problems with a lambda. error CS1977: Cannot use a lambda expression as an argument to a dynamically dispatched operation without first c...
Chuipek asked 24/7, 2017 at 15:52

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Any idea why AWS Lambda functions are unable to publish messages to RabbitMQ using the amqp protocol? (I'm using the node.js runtime with the node amqplib runtime) When using the code from my loc...
Beaux asked 18/8, 2016 at 8:49

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For example: private String test(Optional myOptional) { myOptional.ifPresent(() -> return "1"); return "0"; } so when I call test(myOptional) it will return "1";
Alimentary asked 3/8, 2017 at 12:45

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I have read multiple post similar to my question, but I still can't figure it out. I have a pandas df that looks like the following (for multiple days): Out[1]: price quantity time 2016-06-08 ...
Dioxide asked 30/6, 2017 at 20:39

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The following prints {'a': 'a', 'b': 'b'}: def foo(a: str = "a", b: str = "b") -> None: print(locals()) foo() # Prints {'a': 'a', 'b': 'b'} Which I'd expect as locals in Py...
Dulciana asked 12/8 at 18:32

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I have developed an application in Next.js. For the backend I have used the api endpoints configured in Nextjs which rest inside pages/api. The api end points quite often return 502(Gateway timeout...
Princeling asked 9/5, 2021 at 11:4

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Below is a recursive lambda expression that can compute the values of Fibonacci sequence both in runtime and during constant evaluation: auto fib = [](this auto && f, auto && p) { ...

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Why would one write a C++ lambda with a name so it can be called from somewhere? Would that not defeat the very purpose of a lambda? Is it better to write a function instead there? If not, why? Wou...
Escapement asked 9/8, 2018 at 6:16

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I just switched to Python from Matlab, and I want to use lambda function to map function f1(x,y) with multiple arguments to one argument function f2(x) for optimization. I want that when I map the...
Lopsided asked 21/9, 2016 at 1:3

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I'm working on project with Java 8 and found one situation which I can't understand. I have code like this: void deleteEntity(Node node) throws SomeException { for (ChildNode child: node.getChil...
Cyrene asked 3/9, 2014 at 11:39

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I have an aggregation statement below: data = data.groupby(['type', 'status', 'name']).agg({ 'one' : np.mean, 'two' : lambda value: 100* ((value>32).sum() / reading.mean()), 'test2': lambda...
Misjoinder asked 8/6, 2015 at 20:12

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I am a beginner in using Lambda expression feature in Java 8. Lambda expressions are pretty well useful in solving programs like Prime number check, factorial etc. However can they be utilized eff...
Dignify asked 2/6, 2015 at 12:16

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#include <iostream> int foo(int x = [](){ static int x = 0; return ++x; }()) { return x; }; int main() { std::cout << foo() << foo(); // prints "12", not "11&qu...
Coruscation asked 1/7 at 4:4

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Can somebody please provide some insights on this? Is the lambda capturing external variables, or is the outside world capturing values produced by the lambdas? What does it mean for a certain vari...
Kiefer asked 13/8, 2015 at 4:2

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This is a question that I wondered about since the lambdas had been introduced in Java, and inspired by a related question, I thought that I might bring it up here, to see whether there are any ide...
Napiform asked 31/3, 2016 at 14:51

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I am writing a parser for a file in Java 8. The file is read using Files.lines and returns a sequential Stream<String>. Each line is mapped to a data object Result like this: Result parse(S...
Solo asked 6/11, 2014 at 12:37

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Here is the code: #include <vector> #include <functional> class TestClass { public: const std::vector<int> &getStuff() const { return callback(); } protected: std:...
Redound asked 20/6 at 12:32

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Lets suppose we were given the following two arrays String[] keys = new String[] {"a", "b", "c", "aa", "d", "b"}; int[] values = new int[...
Zinc asked 26/10, 2017 at 7:30

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Consider this simple self-contained code: template<typename T> void foo(); void bar() { int i; auto l = [&i]() -> decltype(auto) { decltype(auto) x = i; foo<decltype(x)>(); ...
Rundlet asked 16/5, 2022 at 23:58

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I was typing the "fun" keyword and then I remembered you don't have to in C# Wouldn't this: List.map (x -> x + 1) [1..10] Be just as expressive as this?: List.map (fun x -> x + 1) [1..10]...
Narrow asked 18/12, 2009 at 0:10

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I have one string say "Aniruddh" and I want to reverse it using lambdas and streams in Java 8. How can I do it?
Rattler asked 27/11, 2017 at 5:58

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I am using Asp.Net Core Identity and trying to simplify some code that projects a list of users and their roles to a ViewModel. This code works, but in trying to simplify it I have gone into a craz...
Doner asked 15/9, 2016 at 18:38

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The code below prints 0, but I expect to see a 1. My conclusion is that lambda expressions are not invoked by actually passing captured parameters to the functions, which is more intuitive. Am I ri...
Blais asked 22/7, 2012 at 10:22

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I am trying to replace the parameter type in a lambda expression from one type to another. I have found other answers on stackoverflow i.e. this one but I have had no luck with them. Imagine for ...
Duff asked 11/7, 2016 at 21:28

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