implicit

I was under the impression that context bounds would work only on methods: trait Target[T] class Post { def pinTo[T : Target](t:T) } apparently context bounds can be used in class (and presumably trait ) too: trait Target[T] class Post[T:Target] { def pintTo[T](t:T) } Now I'm confused as to how the evidence can be provided to Post ? class Business implicit object ev extends Target[Business] // is implicit necessary here ? val p = new Post[Business] // ?? how do I provide ev ? related to Modeling a binary relationship between two types The A: Foo notation for context bounds is only a shortcut

Had a coworker ask me this, and in my brain befuddled state I didn't have an answer: Why is it that you can do: string ham = "ham " + 4; But not: string ham = 4; If there's an implicit cast/operation for string conversion when you are concatenating , why not the same when assigning it as a string? (Without doing some operator overloading, of course) When concatenating the compiler turns the statement "ham" + 4 into a call to String.Concat , which takes two object parameters, so the value 4 is boxed and then ToString is called on that. For the assignment there is no implicit conversion from int

I would expect the next three lines of code to be the same: public static void TestVarCoalescing(DateTime? nullableDateTime) { var dateTimeNullable1 = nullableDateTime.HasValue ? nullableDateTime : DateTime.Now; var dateTimeNullable2 = nullableDateTime != null ? nullableDateTime : DateTime.Now; var dateTimeWhatType = nullableDateTime ?? DateTime.Now; } In all cases, I assign nullableDateTime to the new variable. I would expect the type of all variables to become DateTime? since that is the type of nullableDateTime . But to my surprise, the type of dateTimeWhatType just becomes DateTime , so

I am trying to make a simple application which will send the user to a specific (system installed) app (system settings, calendar, browser, etc.) when clicked by the user from the home screen or app drawer. For instance, I am currently trying to open the system settings whenever my app is launched, just like a shortcut for settings does. Is it possible to implement this the way I want it? Does anyone have any suggestions? Here is my code: import android.app.Activity; import android.content.Intent; import android.content.pm.PackageManager; public class MainActivity extends Activity { public

During daily Scala coding I faced an issue that Scala implicits resolution depends on declaration order. A simple example: object example extends App { trait FooTypeClass[T] { def foo: T } def bar[T](implicit tc: FooTypeClass[T]) = println(tc.foo) class A { // bar[A] doesn't compile } object A { implicit object aFoo extends FooTypeClass[A] { def foo: A = new A { override def toString = "a" } } } bar[A] } It does compile, but if I uncomment the commented line, it won't find the required implicit in scope. So, to make it compile I should place object A declaration before class A . That means my

TLDR : I have two templatized classes Outer and Inner . Inner<X> can be implicitly constructed from X , and Outer<Y> can be implicitly constructed from Y . Should Outer<Inner<X>> = X() work? More details: Suppose I have the following two classes: template<typename T> class Inner { public: Inner(const T& value) {} Inner(T&& value) {} }; template<typename T> class Outer { public: Outer(const T& value) {} Outer(T&& value) {} }; Consider the following function: struct SomeType{}; Outer<Inner<SomeType>> DoSomethingFails() { SomeType value; return value; } g++ complains: no viable conversion from