After digging into the Java SE 8 Final Specification I’m able to answer my questions. (1) In response to my first question Is there any way to annotate a lambda expression similar to annotating a corresponding anonymous class, so one gets the expected “Hello World” output in the example above? No. When annotating the Class … Read more
Have you tried using Expression.Convert? That will add the boxing/lifting/etc conversion. Expression conversion = Expression.Convert(expression, typeof(object)); func = Expression.Lambda<Func<T, Object>>(conversion, parameterExpression).Compile();
For those interested in the outcome: I was missing a simple Using statement at the head of my code. using System.Linq; This fixed it right up.
I don’t think you can get much better than this: .collect(Collectors.toMap(keyMapper, valueMapper, (v1,v2) ->{ throw new RuntimeException(String.format(“Duplicate key for values %s and %s”, v1, v2));}, TreeMap::new)); where the throw lambda is the same as throwingMerger() but I can’t directly call that since it’s package private (you can of course always make your own static method … Read more
Yes, they can. Starting with C++23 you can use the explicit this parameter: auto factorial = [](this auto self, int i) { return (i == 1) ? 1 : i * self(i – 1); }; With previous C++ standards, you can store the lambda in a variable and reference that variable (although you cannot declare … Read more
The problem is that topAgents is dynamic – so your ToList() call is dynamic, and so is Select. That has issues that: you can’t use lambda expressions for dynamic calls like this; dynamic calls don’t find extension methods anyway. Fortunately, the operations don’t need to be dynamic just because the element type is dynamic. You … Read more
Closures, lambdas, and anonymous functions are not necessarily the same thing. An anonymous function is any function that doesn’t have (or, at least, need) its own name. A closure is a function that can access variables that were in its lexical scope when it was declared, even after they have fallen out of scope. Anonymous … Read more
To get a range from a Stream<T>, you can use skip(long n) to first skip a set number of elements, and then you can call limit(long n) to only take a specific amount of items. Consider a stream with 10 elements, then to get elements 3 to 7, you would normally call from a List: … Read more
But, a 1-arg constructor for T that takes a String is compatible with Function<String,T>: Function<String, Foo> fooSupplier = Foo::new; Which constructor is selected is treated as an overload selection problem, based on the shape of the target type.
This is known as vacuous truth. All members of an empty collection satisfy your condition; after all, can you point to one that doesn’t? Similarly, anyMatch returns false, because you can’t find an element of your collection that does match the condition. This is confusing to a lot of people, but it turns out to … Read more