implicit Questions
1
Solved
I'm having some trouble with an implicit view. I suspect this is quite trivial and may have some embarassingly easy answer. I have a situation like this, along with (obviously, unsuccessful) attemp...
Drumbeat asked 19/9, 2020 at 2:6
4
Solved
I have some code with nested calls to flatMap like so:
foo.flatMap(implicit f => bar(123).flatMap(b =>
/* and so on... implicit f is still in scope here.*/
))
Normally, one would write th...
By asked 28/12, 2012 at 17:21
2
Solved
I am writing a small Scala Program which should:
Read a file (line by line) from a local FS
Parse from each line three double values
Make instances of a case class based on those three values
Pass...
3
Solved
When I have a function in Scala:
def toString[T: Show](xs: T*): String = paths.map(_.show).mkString
And the following type class instances in scope:
implicit val showA: Show[MyTypeA]
implicit val ...
Tc asked 12/8, 2020 at 16:3
0
I thought that if the following compiles:
implicitly[X => Y]
than so will this:
(??? :X) :Y
It turns out I was wrong. Backstory: I toyed with an implementation of type unions:
private[this] va...
Laveralavergne asked 20/7, 2020 at 19:21
1
Solved
Why this scala code
case class Foo[T]() {
def bar(tt: T): Unit = ???
def bar_(s: String)(implicit ev : T =:= String): Unit = bar(s)
}
triggers this compilation error
[error] type mismatch;
[erro...
Tussock asked 11/7, 2020 at 12:44
2
The scala language specification, section 7.2 is about implicit scope:
It explains that implicit scope are the modules associated in some way with the parts of type T. What the parts of T are is l...
3
Solved
I'm interested if I can create method with similar idea:
def myMethod[T](param: T)(implicit oneOf: Either[TypeClass1[T], TypeClass2[T]]) = oneOf match ...
I've tried to use default parameters (I...
1
Solved
trying to implement Kleisli category for a made-up Partial type in Scala (reading Bartosz Milewski's "category theory for programmers", that's exersize for chapter 4)
object Kleisli {
ty...
Escudo asked 6/7, 2020 at 7:47
1
The following simple code:
implicit val a: String = "abc"
implicitly[a.type]
fails to compile despite that a is totally in the scope and consistent in type:
Error:(9, 13) could not fi...
1
Solved
Here is a simplified version of my code.
How can I avoid to call asInstanceOf (because it is a smell for a poorly design solution) ?
sealed trait Location
final case class Single(bucket: String) ex...
Scuff asked 3/7, 2020 at 13:20
1
Solved
Assuming that A class called 'summoner' was defined, that is capable of summoning implicit views from the scope:
case class Summoner[R]() {
def summon[T](v: T)(implicit ev: T => R): R = ev(v)...
1
Solved
Assuming that a class Thing is defined, and an operation + is associated with a type class:
trait TypeClass[X, Y] {
type Out
def v: Out
}
object TypeClass {
implicit def summon[X <: In...
1
Solved
I am learning about Scala on my own and ran into this. Following on from the excellent answers at Link, suppose I have the following code:
object Example extends App {
val x = Seq(1, 2, 3)
val y...
Impudicity asked 13/6, 2020 at 21:28
1
Solved
This code results in NullPointerException:
import anotherpackage.MyContext
import anotherpackage.builders.aMyContext
case class Context(id: String)
object Context {
implicit def `ContextHolder t...
1
Solved
I have a somewhat complex typeclass situation in the following format:
sealed trait TypeClass[S <: MyType] {
type Out <: MyType
}
sealed trait LowPriorityTypeClass {
// Case: OtherTypeCla...
2
Solved
A very simple use case, let's say I have a class Foo that is accepting 2 parameters 1 is normal parameter and 1 is implicit.
class Foo(val msg: String, implicit val n: Int) {
def multiplier = ms...
1
Solved
I was going through Scala 3 documentation. They have introduced given keyword which is considered as the alternative of Scala 2 implicit.
The code is here
trait Ord[T] {
def compare(x: T, y: T): ...
6
Solved
I would like to plot implicit equations (of the form f(x, y)=g(x, y) eg. X^y=y^x) in Matplotlib. Is this possible?
Orpington asked 20/3, 2010 at 20:0
3
Solved
1
Solved
This code gives an error:
public class A<T>
{
public class B<T1> : A<T1>
{
public static implicit operator bool(B<T1> b) => true;
}
}
But if I separate the clas...
Constructivism asked 22/12, 2019 at 13:12
2
Solved
In one file, I have:
trait JsonSchema[T] {
val propertyType: String
override def toString: String = propertyType
}
object JsonSchema {
implicit def stringSchema: JsonSchema[String] = new Json...
1
Solved
In scala language, implicit resolution is often done in compile-time and sometimes throws obfuscating error information, one famous example of such error is when shapeless Generic throws error info...
Malebranche asked 15/12, 2019 at 21:43
1
Solved
I have a method with implicits:
def f(x: String)(implicit dispatcher: ExecutionContextExecutor, mat: ActorMaterializer) = ???
And I want to create a helper method like:
def g1(y: String) = f("u...
0
When I try to create an extension for the class via implicit class and overload existing generic method, it fails with compilation error:
error: overloaded method value getAs with alternatives:
(...
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