implicit Questions
1
Solved
I'm using doobie to query some data and everything works fine, like this:
case class Usuario(var documento: String, var nombre: String, var contrasena: String)
def getUsuario(doc: String) =
sql...
Otiliaotina asked 23/10, 2019 at 21:6
2
Consider the default codec as offered in the io package.
implicitly[io.Codec].name //res0: String = UTF-8
It's a "low priority" implicit so it's easy to override without ambiguity.
implicit val...
Hun asked 1/4, 2019 at 19:29
1
Solved
I have a typeclass Search, which has an instance Search[A] if we have a TypeClass1[A] or a TypeClass2[A] instance. With preference given to the 1 instance.
The following compiles:
trait TypeClass...
Egoist asked 14/9, 2019 at 8:40
1
I thought Implicit linking loads a DLL as soon as the application starts because it is also called "load-time dynamic linking". But I found some strange explanations below from the link here(https:...
1
Solved
I am trying to implement a method that does parameterized folding on a HList provided by the caller. The HList can have any number of elements (> 0) of the same type.
val list = "a" :: "b" :: "c" ...
3
Solved
I have a customized compare methods that takes two parameters. One of them are expected to be implicitly convertible to another:
object Test extends App {
def compare[T1, T2](a: T1, b: T2)(implic...
Coddle asked 6/8, 2019 at 22:45
4
Solved
I am learning Scala and I was trying to create a type class to solve the "Every animal eats food, but the type of food depends on the animal" problem. I have an Eats type class with context bounds:...
Salchunas asked 13/7, 2019 at 10:14
1
Consider the following setup:
trait Foo[A]
object Foo extends Priority2
trait Priority0 {
implicit def foo1: Foo[Int] = new Foo[Int] {}
}
trait Priority1 extends Priority0 {
implicit def foo2: ...
7
Solved
The following code generates a compile error in Xcode:
template <typename T>
struct Foo
{
Foo(T Value)
{
}
};
int main()
{
Foo MyFoo(123);
return 0;
}
error: missing template argume...
1
Solved
Consider this code:
trait TypeOr[E, F] {
type T
}
implicit def noneq2[E, F](implicit ev: E =!= F): TypeOr[E, F] = new TypeOr[E, F] {
type T = (E, F)
}
sealed trait Error[+E, +A]
case cl...
Stardom asked 10/4, 2019 at 9:38
3
Ctrl + Q to find implicit conversion
Shift + Cmd + P to find the place of an implicit parameter instance
How do I find where an implicit value/def is used?
Bouncy asked 27/10, 2017 at 9:53
2
Solved
This code fails to compile:
object Foo {
implicit def toString(i: Int): String = i.toString
def foo(x: String) = println(x)
foo(23)
}
Above code fails to compile with following error:
erro...
1
Solved
In my project, I have a type A, used for arguments in a few places, where I want a bunch of types automatically converted to that type. I've implemented this using a few implicit classes in the com...
Wigwag asked 21/2, 2019 at 10:3
1
I am working with type classes and have problems auto-deriving them for types that unrelatedly extends extra (marker/indicator) traits. It is hard to explain, but this minimal example should make i...
Candlelight asked 20/2, 2019 at 21:6
1
I am using circe to serialize/deserialize some reasonably large models, where each leaf field is a strong type (e.g. case class FirstName(value: String) extends AnyVal).
Implicit resolution/deriva...
1
Scala allows to define types using the type keyword, which usually have slightly different meaning and purpose depending on when they are declared.
If you use type inside an object or a package ob...
Ganda asked 10/1, 2019 at 21:59
2
(I am fairly new to Scala, hope this isn't a stupid question.)
From what I can see, declaring a parameter to a function implicit has two (related, but quite different) uses:
It makes explicitly ...
1
Solved
Given following code:
val javaLong: java.lang.Long = null
val opt: Option[Long] = Option(javaLong)
I expected opt to be None but for some reason it is Some(0). I also found this bug and it appea...
1
Solved
I'm working with Slick's GetResult typeclass and wanted to use Shapeless to derive instances of GetResult[Option[(A, B, C...)]]
What I want:
Given an implicit GetResult[Option[A]], GetResult[Opt...
3
I use Scala implicit classes to extend objects I work with frequently. As an example, I have a method similar to this defined on Spark DataFrame:
implicit class DataFrameExtensions(df: DataFrame) ...
Dormitory asked 14/5, 2018 at 13:15
11
As I understand from this blog post "type classes" in Scala is just a "pattern" implemented with traits and implicit adapters.
As the blog says if I have trait A and an adapter B -> A then I ca...
3
There seems to be a lot of enthusiasm among Scala bloggers lately for the type classes pattern, in which a simple class has functionality added to it by an additional class conforming to some trait...
Udelle asked 15/7, 2010 at 13:35
2
Solved
I am trying to write a text game and I have run into an error in the function I am defining that lets you basically spend your skill points after you make your character. At first, the error ...
2
Solved
I recently started to work on play & reactive mongo. Referred the reactive mongo documentation to create a SimpleAlbum. When I run the play app I am getting an error like "Implicit modifier can...
1
Guys, I have started to work on selenium web driver. You can assume I am a beginner. At the moment I am having difficulties in implementing the implicit wait command in my code (C#). it is not work...
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