Scalaz provides type classes and purely functional data structures for Scala
Questions tagged [scalaz7]
102 questions
4
votes
1 answer
How to fix sbt's [warn] Skipped generating '
When I run makePom in sbt I get:
[warn] Skipped generating '
Robin Green
- 32,079
- 16
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4
votes
1 answer
Why does this Scalaz 7 enumerator leak memory?
The following definition results in a memory leak:
def enumIterator1[E, F[_]: Monad](x: => Iterator[E]) : EnumeratorT[E, F] =
new EnumeratorT[E, F] {
def apply[A] = (s: StepT[E, F, A]) => {
def go(xs: Iterator[E]): IterateeT[E, F, A] =
…
Aaron Novstrup
- 20,967
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4
votes
2 answers
How to help Scalaz with type inference and 2 type parameters
I have something called a Generator:
trait Generator[A, B] {
def generate(in: Seq[A]): Seq[B]
}
I can provide a Bind instance for this generator:
object Generator {
implicit def generatorBind[T]: Bind[({type l[B] = Generator[T, B]})#l] = new…
Eric
- 15,494
- 38
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3
votes
1 answer
Scalaz Reader to ReaderT
A function which I cannot change returns Scalaz Reader,
type Action[A] = Reader[Session, A]
def findAccount(s: String): Action[Account] =
Reader((session: Session) => Account(s))
I want create a new function based on findAccount(...) to return…
thlim
- 2,908
- 3
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3
votes
1 answer
Are unboxed tagged types safe?
I've recently heard about unboxed tagged types in scala and while I was trying to learn how exactly it works, I've found this question that points to problems the implementation in scalaz had. One of the consequences of the fix was having to…
andrepnh
- 933
- 8
- 21
3
votes
3 answers
What's the new name for map2 in Scalaz 7?
Jordan West in this presentation from Scalamachine clearly speaks about map2 function. Turns out the function was available in Scalaz 6 but I can't find it or any equivalent in Scalaz 7.
E.g. I would like to be able to run this code:
List(Some(1),…
mjaskowski
- 1,479
- 1
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- 16
3
votes
1 answer
What does λ[α =>F] mean?
I'm learning Scalaz recently. I would like to know how λ[α =>F] works?
scala> Applicative[λ[α => Int]].point(10)
res45: Int = 0
scala> Applicative[λ[α => String]].point(10)
res46: String = ""
I can understand λ means some type here, but I could…
Binzi Cao
- 1,075
- 5
- 14
3
votes
2 answers
How to implement parametric lenses that change type of state
So in scala we have the typical Lens signature as:
case class Lens[O,V](get: O => V, set: (O,V) => O)
But as you can see, it only updates and sets values of the same type, it does not set one type for another. What I have in mind is something more…
user1553111
3
votes
1 answer
How do I declare a scala case class to be an instance of Scalaz's Semigroup?
I have a type, defined as follows:
import scalaz._, Scalaz._
case class MyInt(i : Int)
I want to make an instance of Semigroup. I tried this:
object MyInt {
implicit def myIntSemigroup: Semigroup[MyInt] = new Semigroup[MyInt] { …
Mersenne Prime
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3
votes
0 answers
Parsing Big XML with Scales Xml (Scala), the functional way - StackOverFlowError using Zippers
Long time lurker, first time poster. Please let me know if my question is not clear.
I have a kinda strange XML file that needs to be parsed (put data inside a class and handle it internally).
I mention it's strange because what anyone would…
mmedina
- 256
- 3
- 9
3
votes
1 answer
Cohesive way to validate a class in Scala using Scalaz 7
My goal is to validate User's fields within the object's applymethod before creating one effective User instance:
case class User(String userName, String password)
object User {
def apply(userValidator: UserValidator):…
Mik378
- 21,881
- 15
- 82
- 180
3
votes
2 answers
Best way to write Scala methods signature dealing with exceptions
In order to handle exceptions in Scala, I prefer avoiding basic try/catch and benefit from functional thinking with Validation from Scalaz (similar to Either type in certain cases).
My application exposes some services. Imagine this method (making…
Mik378
- 21,881
- 15
- 82
- 180
3
votes
1 answer
point reader monad scala
is there a way, how to easily point a value in Reader context?
I can use Reader object and ignore the context:Reader {
_ ⇒ 3
}
Scalaz seems to have a method point for this specifically. I see, that is defined on Applicative. I suppose, that there…
ryskajakub
- 6,351
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3
votes
1 answer
Where is the type @> in scalaz source code?
I've been reading the source for scalaz's Lenses, which you can find at https://github.com/scalaz/scalaz/blob/scalaz-seven/core/src/main/scala/scalaz/Lens.scala
Starting at line 303, there are functions that return values of type @>[A,B]. Is this…
Mark
- 5,286
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- 73
2
votes
1 answer
Specifying an execution context for Monad[Future] when using EitherT in Scalaz 7
I've been trying to tidy up some code which uses multiple functions that all return the type Future[Either[String, A]].
These functions don't compose neatly in a for comprehension because of the problem of having to peak inside the Future and then…
justinhj
- 11,147
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