Questions tagged [value-class]
62 questions
16
votes
1 answer
Why does the transpose function change numeric to character in R?
I've constructed a simple matrix in Excel with some character values and some numeric values (Screenshot of data as set up in Excel). I read it into R using the openxlsx package like so:
library(openxlsx)
data <-…
Morten Nielsen
- 325
- 2
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15
votes
5 answers
Value classes introduce unwanted public methods
Looking at some scala-docs of my libraries, it appeared to me that there is some unwanted noise from value classes. For example:
implicit class RichInt(val i: Int) extends AnyVal {
def squared = i * i
}
This introduces an unwanted symbol i:
4.i …
0__
- 66,707
- 21
- 171
- 266
14
votes
5 answers
Value-based Classes confusion
I'm seeking some clarification to the definition of Value-based Classes. I can't imagine, how is the last bullet point (6) supposed to work together with the first one
(1) they are final and immutable (though may contain references to mutable…
maaartinus
- 44,714
- 32
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13
votes
1 answer
How do you enrich value classes without overhead?
Scala 2.10 introduces value classes, which you specify by making your class extend AnyVal. There are many restrictions on value classes, but one of their huge advantages is that they allow extension methods without the penalty of creating a new…
Rex Kerr
- 166,841
- 26
- 322
- 407
11
votes
4 answers
android Room with kotlin value class?
I'm trying to use a room entity with a value class:
@JvmInline
value class UserToken(val token: String)
and the entity:
@Entity(tableName = TABLE_AUTH_TOKEN)
data class TokenEntity(
@PrimaryKey val id: Int = 0,
val token: UserToken
)
I get the…
TootsieRockNRoll
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- 2
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- 50
11
votes
1 answer
Is there a way to get a warning when a Scala Value Class needs to become instantiated?
In the documentation about Scala value classes, it is mentioned that there are three cases when a value class needs to actually be allocated an instance:
Allocation Summary
A value class is actually instantiated when:
a value class is treated as…
Prikso NAI
- 2,592
- 4
- 16
- 29
10
votes
1 answer
Elegant grouping of implicit value classes
I'm writing a set of implicit Scala wrapper classes for an existing Java library (so that I can decorate that library to make it more convenient for Scala developers).
As a trivial example, let's say that the Java library (which I can't modify) has…
Mike Allen
- 8,139
- 2
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- 46
9
votes
1 answer
Does Inheritance in implicit value classes introduce an overhead?
I want to apply scala's value classes to one of my projects because they enable me to enrich certain primitive types without great overhead (I hope) and stay type-safe.
object Position {
implicit class Pos( val i: Int ) extends AnyVal with…
peri4n
- 1,389
- 13
- 24
8
votes
1 answer
Result type in structural refinement may not refer to a user-defined value class
When I define Wrapper as value class(extending AnyVal):
class Wrapper(val string: String) extends AnyVal
def wrapperHolder(w: Wrapper): {def wrapper: Wrapper} = new {
def wrapper: Wrapper = w
}
I have following compile error for…
mkUltra
- 2,828
- 1
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- 47
8
votes
3 answers
Scala value class, use cases
I know value class in scala inline the operation at compiler time.
maybe like this
case class A(i: Int) extends AnyVal {
def +(that: A) = A(this.i + that.i)
}
A(1) + A(2) // After compile it equals to 1 + 2
But It seems not a big deal to…
Wonpyo Park
- 301
- 3
- 11
7
votes
1 answer
Implicit conversion between Scala.Long and Java.lang.Long in collections
I'm using JavaConverters to go from a Java SortedSet to a Vector.
val lines = function.getInstructions.asScala.toVector
My getInstructions function returns an ArrayList of java.lang.Long, yet the consuming code requires Scala.Long. Is there a…
Steve H.
- 253
- 1
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- 12
6
votes
1 answer
Convert sequence of AnyVal case class (Seq[T <: AnyVal]) to its runtime representation efficiently
Assuming I have a value case class
case class Id(i:Int) extends AnyVal
and a sequence containing this value case class
Seq(Id(1), Id(2), Id(3))
is there a way of converting those values into Int without that there is a need of iteration over the…
Big_Foot1989
- 311
- 1
- 3
- 11
6
votes
1 answer
Value classes, universal traits and the necessity of instantiation
In the specification of value classes, it says:
A value class can only extend universal traits and cannot be extended itself. A universal trait is a trait that extends Any, only has defs as members, and does no initialization. Universal traits…
oxbow_lakes
- 133,303
- 56
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- 449
5
votes
1 answer
Kotlin inline value class - cannot override hashCode() function
I just cannot override hashCode() function on value class.
minimal example (I know that in this example there is no need to override it...)
@JvmInline
value class Identifier(val value: String){
override fun hashCode(): Int =…
user17211472
- 55
- 5
5
votes
0 answers
Value classes as structural type members
Here is the simplified code:
class Value(val value: Int) extends AnyVal
val v = new Value(1)
val x = new { val f: Int = v.value }
println(x.f)
val y = new { val f: Value = v }
println(y.f)
Error: Result type in structural refinement may not…
xiagao1982
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