Questions tagged [implicit]
An implicit in Scala is a function applied or a parameter provided without explicitly appearing in the source code.
implicit
1,796
questions
0
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1
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54
views
ZIO Quill: Can't find implicit SchemaMeta for type models.Pet
I'm currently working on a pet store application using ZIO and Quill. As part of my learning process, I've set up a local H2 database and configured it to store pet information. However, I'm ...
2
votes
2
answers
66
views
How to define a "fallback" implicit?
Consider a tapir.Codec object (this is how I encountered this problem, but I don't think it has much to do with tapir specifically, it is just about implicit resolution priority in general), it has a ...
- 40.1k
0
votes
1
answer
81
views
In Scala 2/3, why can't unboxing or view bounds be chained (as in OCaml), and how to fix/circumvent it?
Considering the following example, derived from the official manual of Scala 3 on Context Abstractions:
https://docs.scala-lang.org/scala3/guides/migration/incompat-contextual-abstractions.html#view-...
- 3,898
1
vote
1
answer
60
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+100
How to test fastparse parsers in a separate class?
I'm writing a parser, something like,
object MyParser:
def int[$: P]: P[Int] = digit.rep(1).!.map(s => s.toInt)
def digit[$: P]: P[Unit] = CharIn("0-9")
Now I'd like to test this in ...
- 2,186
0
votes
0
answers
51
views
Scanamo Paginated Query Issues
Need example of a method to create paginated query on dynamoDb using scala's, Scanamo library
I am trying to create to create a method which performs paginated queries on dynamodb table using a query ...
- 1
0
votes
0
answers
61
views
All partial unification algorithms failed on implicit conversion from functions - How to improve in Scala?
Here is a simple example:
object UnificationOnConversionFromFn {
trait :=>[I, R]
implicit def fromVanilla[I, R](
vanilla: I => R
): I :=> R = ??? // fail
implicit def ...
- 3,898
1
vote
1
answer
96
views
Implicit resolution failure when multiple instances present, despite having different types
My goal is to implement a Schema[T] (from scala-jsonschema) and Writes[T] (from play-json) for a handful of T classes whose companions I can't modify. My sub-goal is to define them close together to ...
- 13.7k
2
votes
0
answers
34
views
Extensions methods using implicits do not compile with Scala 3
Following code compiles fine with Scala 2.13.12, but not with Scala 3.3.1:
import scala.language.implicitConversions
object Types {
trait Vector3f
implicit class Vector3fOps(v: Vector3f) {
...
- 33.9k
2
votes
0
answers
50
views
Scala 3 given/implicit resolution doesn't work as expected
I'm working on the Chapter 11 Case Study: CRDTs from the excellent book "Scala with Cats". The code in the book is written using Scala 2, but I've modified it for Scala 3, specifically 3.3.1....
- 23.1k
1
vote
1
answer
36
views
Recursive value needs type error in Scala 3 implicit parameter
I'm trying to compile the following code in Scala 3 (worked on Scala 2.13):
import scala.concurrent.duration._
@main
def main(): Unit = {
case class AAA(d: FiniteDuration)
val duration1 = 5....
- 2,523
1
vote
2
answers
68
views
c# Implicitly typed arrays behind the scenes
Can someone explain how the compiler proceeds here to find the "common" type (double).
I assume the IConvertible plays a role here?
private static void Main(string[] args)
{
var nrColl = ...
- 25
1
vote
1
answer
64
views
HList Ops - how are type classes constracted?
Can someone explain why this code compiles and works like a charm:
val a = true :: Some(5) :: true :: HNil
a.select[Some[Int]] // Some(5)
but this one fails:
def foo[HL ...
0
votes
0
answers
23
views
Implicit equation plotting
I’m not a python expert, just a beginner, I would like to know how I could code and plot the equation shown here by using the implicit equation option??. This is my attempt but not sure how to plot it....
0
votes
0
answers
50
views
It is possible to provider some default given contextual for class method?
Suppose I have defined a class Test:
import scala.collection.{IterableFactory, Factory}
class Test:
def p1[C[_]](xs: Int*)(using f: Factory[Int, C[Int]]): C[Int] = f.fromSpecific(xs)
def p2[C[...
- 1,529
0
votes
2
answers
72
views
implicit wait in selenium
I am very confused about how to use implicit wait in selenium
driver.manage().timeouts().implicitlyWait(1, TimeUnit.SECONDS);
driver.manage().timeouts().pageLoadTimeout(4, TimeUnit.SECONDS);
I saw ...
- 21
1
vote
1
answer
120
views
How to share url from android app with image preview
I want to create a share sheet just like the share exist in google store , as you can see here is google store sample
currently I am using this code :
ShareCompat.IntentBuilder(context)
....
1
vote
1
answer
133
views
Adjusting axis’ ticks in plotting with SymPy
Here is the problem:
I have two implicit functions F and G. I am trying to find a way to plot them using SymPy.
My question is, how to adjust ticks on x- and y-axis, so I can see a crossing point of ...
- 15
2
votes
1
answer
28
views
Generic type BoundedComponent struct
I want to do a struct for boundedElements like number that has a max and min value. However I'm stuck on how to do this.
Here is an example of a property. The setfield method is just a method to set a ...
0
votes
0
answers
37
views
Scala - Trying to wrap occurrences of booleans using implicits
I'm new to implicits in scala and am sure there is a way to do this but have tried everything I can think of.
I have a trait:
trait WrappedDataframe[T] extends Rep[DataFrame]
def apply[S](colName: ...
- 133
0
votes
2
answers
118
views
how to use implicit intent in android
In my application, I created two activities. In activity1, I created a button, set event:
activity2, I created, and write in manifest:
when i click to the button in activity1, error was throw:
Why? ...
1
vote
2
answers
74
views
Question about implicit class argument in Java method reference
In Java, the class portion of a method reference can become the first argument of the function. I've seen lots of examples in working code. But I wondered where in the Java Language Specification this ...
- 207
0
votes
0
answers
50
views
Use default implicit and an overloaded function
Here is what I am trying to achieve:
class SomeTest {
...
verify(foo).bar(any)
verify(foo, times(2)).baz(any)
..
inOrder(foo) { implicit order =>
verify(foo).bar(any)
verify(...
- 40.1k
3
votes
2
answers
164
views
How to properly use collection factories in scala 2.13?
Something like this:
implicit class PairOps[A, B, C[X] <: Iterable[X]](val c: C[(A,B)]) extends AnyVal {
def swap = c.map { case (a, b) => (b, a) }
}
Kinda works ... except that val foo: ...
- 40.1k
-1
votes
1
answer
71
views
Implicitplot with three colors in Maple
I am using implicitplot in Maple using this command:
implicitplot(diffr, 0. .. 1, 0. .. 1.0, filledregions = true, coloring = [cyan, yellow]);
So, when diffr<0 and diffr>0, I received a diagram ...
2
votes
1
answer
67
views
Should I explicitly implement getName(), getAddress(), and setAddress() in my Kotlin code based on the UML?
I have implemented the following UML in Kotlin, and I am now considering whether I should explicitly implement the methods getName(), getAddress(), and setAddress() in my code, as they are mentioned ...
- 434
1
vote
1
answer
64
views
In Scala 3, is it possible to summon implicits based on refined type?
Considering the following example:
{
trait Gen {
type S
type Ext
}
type GenAux[_S] = Gen { type S = _S }
trait Gen_Fallback1 {
given [_S]: GenAux[...
- 3,898
1
vote
2
answers
363
views
Could not find implicit value for parameter F: cats.Applicative[F] with Sync and Temporal
Basically, I just want to add a sleep somewhere, but I don't understand how to provide the implicit Applicative needed.
I'm using cats effect 3.5.
It's totally new to me.
I have been using ZIO for 2 ...
- 147
0
votes
1
answer
158
views
why std::make_unique<A>(*this) could call an implicitly-declared copy-constructor of A
The source question is from Usage of this* in make_unique
The code is below, and the best answer says:
In clone(), *this is an lvalue-reference to A, so you are constructing a A from an (lvalue-...
- 27
0
votes
0
answers
39
views
Idk where I supposedly declared my function as a different type (C) [duplicate]
Well I got this issue and I don't get why? If someone could explain I'm just trying to learn C lmao
I don't even have a clue of where I'm supposed to let it implicitly declare this function as ...
1
vote
1
answer
47
views
Creating syntactic sugar for a scala argument to give the illusion of a different type
I am creating a library and am exposing a class called A that has in it defined a function func(f: SomeType => A). It is imperative that func is called with the following syntax:
val x = new A()
...
- 133
0
votes
0
answers
91
views
Folding a tuple in Scala 3
Working with ZIO and Scala 3, I want to create a utility function productElementsLayer that for a given type A <: Product produces a value of type ZLayer[A, Nothing, (E1, ..., EN) where (E1, ..., ...
- 3,208
2
votes
2
answers
2k
views
Playwright clicks element (drop down) before it is ready resulting in the drop down not opening
I have a product page containing a product with quantity options. There is a drop down to select the quantities. I want to click this to open it and select an option. The steps are simple:
Load page
...
- 31
19
votes
4
answers
791
views
Why in C# an explicit decimal => long conversion operator is called implicitly, losing precision? [duplicate]
The following C# program silently and implicitly calls an explicit decimal-to-long conversion operator, losing precision.
I don't understand why this happens. As far as I understand, in C# explicit ...
- 4,495
0
votes
0
answers
61
views
Scala: Type Mismatch error when passing argument based on the same type
I have a basic scala issue:
I defined a custom function to add to Dataset[Row] that lets me create my own WrappedDataset and used an implicit function to achieve that:
class CustomFunctions(dataset: ...
- 133
0
votes
2
answers
71
views
could not find implicit value for evidence parameter of type cats.MonadThrow[sttp.client3.Identity]
I'm considering using stac4s as a STAC client in our Scala project but boy, is it giving me a hard time. The use of cats, monads and all that fancy stuff is very daunting and there's no documentation ...
- 3,592
0
votes
1
answer
336
views
Converting case class object to json string using spray json
I am new to scala and I need to convert a case class object to a json string using spray json. The case class look as below:
case class DriverDetails(userId : String, names : Option[List[String]], ...
- 23
0
votes
1
answer
52
views
Why can't the compiler chain conversions?
Let T1, T2, T3 be three types. We also define two given instances of the Conversion class so that the compiler can go from T1 to T2 and from T2 to T3.
The following code then compiles fine:
type T1
...
- 360
0
votes
1
answer
49
views
Implicit conversion differencies
The following works:
case class Fraction(d: Int, n: Int) {
def *(other: Fraction) = Fraction(d * other.d, n * other.n)
}
implicit val int2fraction: Int => Fraction = { x => Fraction(x, 1) }
...
- 24.3k
0
votes
1
answer
146
views
No implicit Ordering defined for ord
I want to define a collection class and require its element being Ordered
Considering the code below:
class MyCollection[K: Ordered[K]] {
def func(seq: Seq[K]): Unit = {
seq.sorted
}
}
The ...
- 3,011
2
votes
2
answers
362
views
Using Postgres enum with Quill
I'm trying to use a Scala 2 enum with Quill, like so:
import io.getquill.MappedEncoding
object MyEnumType extends Enumeration {
type MyEnumType = Value
val ONE, TWO, THREE = Value
implicit ...
- 2,000
0
votes
1
answer
130
views
How import spark.sqlContext.implicits._ works in scala?
I'm new in Scala
Here's what I'm trying to understand
This code snippet gives me RDD[Int], not give option to use toDF
var input = spark.sparkContext.parallelize(List(1,2,3,4,5,6,7,8,9))
But when I ...
- 29
0
votes
1
answer
263
views
Doobie cannot find or construct a Read instance for Type of case class with Timestamp
Given a case class representation of a data row with a java.sql.Timestamp:
case class ExampleRow(id: String, ts: Timestamp)
And query expecting an ExampleRow:
import doobie._
import doobie....
- 17.7k
4
votes
2
answers
72
views
Proving that a match type resolves to a specific concrete type
I am trying to create an implementation of a trait that uses a match type, where the right-hand-side of that match type is known in advance. However, I can't seem to get the compiler to accept my &...
- 53
0
votes
2
answers
45
views
Implicit declaration of function // Problem with a createString function
Hey Guys i need your help. I am learning for my C-exam in two days. For that i had written a little code for a simple list.
My Problem is that i get every time the same error: "implicit ...
- 1
1
vote
1
answer
65
views
Insertion into scylladb table using phantom library in scala not working
I'm new to ScyllaDB, and trying to perform CRUD operations using phantom library in scala.
First I've made 3-node cluster and its running fine.
Datacenter: DC1
===============
Status=Up/Down
|/ State=...
- 121
0
votes
1
answer
105
views
Parametric polymorphism issue with spark implicits, value toDF is not a member of Seq[T]
This is on scala 2.12.10 and spark 2.4.8. I am trying to define a trait as follows with a method that can convert an array of some case class to be converted to a dataframe. The type parameter is ...
- 596
1
vote
1
answer
812
views
How to add extension method to a singleton object in scala 2?
I've stumbled upon this thread and there @prolativ provided some fancy scala 3 syntax for creating extension methods for objects
extension (int: Int.type)
def unapply(s: String): Option[Int] = s....
- 15
2
votes
1
answer
236
views
"Deferred inline method `foo` in trait `Foo` cannot be invoked": Pairs
I was just experimenting with the behavior of givens and inline in Scala 3.2.2, and ran into the following example:
trait Max[X]:
inline def max(a: X, b: X): X
inline given maxForDoubles: Max[...
- 44.5k
5
votes
2
answers
438
views
How to summon a `given` member?
Suppose that I have some typeclass
trait FooBar[X]
and an instance of FooBar[Int]:
given intIsFooBar: FooBar[Int] = new FooBar {}
Now, suppose that I have an interface Intf that has some member type ...
- 44.5k
1
vote
1
answer
209
views
Type negation in Scala 3
Is it possible to implement fail proof Not[A] type in Scala 3?
Here is a question asked some years ago: how-can-i-have-a-negation-type-in-scala.
Unfortunately, a solution based on 'not given A <:&...
- 2,210