Just use the qualified return syntax: return@fetchUpcomingTrips. In Kotlin, return inside a lambda means return from the innermost nesting fun (ignoring lambdas), and it is not allowed in lambdas that are not inlined. The return@label syntax is used to specify the scope to return from. You can use the name of the function the lambda … Read more
First define the lambda object, then pass it to the template’s type using decltype and also pass it directly to the constructor. auto comp = []( adjist a, adjlist b ) { return a.second > b.second; }; priority_queue< adjlist_edge , vector<adjlist_edge>, decltype( comp ) > adjlist_pq( comp );
The lifetime is exactly what it would be if you replaced your lambda with a hand-rolled functor: struct lambda { lambda(int x) : x(x) { } int operator ()(int y) { return x + y; } private: int x; }; std::function<int(int)> meta_add(int x) { lambda add(x); return add; } The object will be created, local … Read more
The RTM version of Entity Framework 4.1 actually includes extension methods in the EntityFramework.dll file, for eager loading with lambda through the Include function. Just include the DLL in your project and you should be able to write code like: var princesses1 = context.Princesses.Include(p => p.Unicorns).ToList(); Remember to add an Import/Using statement to include the … Read more
Yes, you can do this by creating a DoubleStream from the array, filtering out the negatives, and converting the stream back to an array. Here is an example: double[] d = {8, 7, -6, 5, -4}; d = Arrays.stream(d).filter(x -> x > 0).toArray(); //d => [8, 7, 5] If you want to filter a reference … Read more
Each variable expressly named in the capture list is captured. The default capture will only capture variables that are both (a) not expressly named in the capture list and (b) used in the body of the lambda expression. If a variable is not expressly named and you don’t use the variable in the lambda expression, … Read more
Optional<User>.ifPresent() takes a Consumer<? super User> as argument. You’re passing it an expression whose type is void. So that doesn’t compile. A Consumer is intended to be implemented as a lambda expression: Optional<User> user = … user.ifPresent(theUser -> doSomethingWithUser(theUser)); Or even simpler, using a method reference: Optional<User> user = … user.ifPresent(this::doSomethingWithUser); This is basically the … Read more
I usually have no problem debugging lambda expressions while using Eclipse or IntelliJ IDEA. Just set a breakpoint and be sure not to inspect the whole lambda expression (inspect only the lambda body). Another approach is to use peek to inspect the elements of the stream: List<Integer> naturals = Arrays.asList(1,2,3,4,5,6,7,8,9,10,11,12,13); naturals.stream() .map(n -> n * … Read more
var query = source.GroupBy(x => new { x.Column1, x.Column2 });
int maxShoeSize = Workers.Where(x => x.CompanyId == 8) .Select(x => x.ShoeSize) .DefaultIfEmpty(0) .Max(); The zero in DefaultIfEmpty is not necessary.