Use dependent types for downcasting?
Here's code I have:
sealed trait Section {
val value:String
type Out
}
case object AUTO_LOANS extends Section{
val value="auto-loans"
type Out = AUTO_LOANS.type
}
case object STUDENT extends Section{
val value="student"
type Out = STUDENT.type
}
object Section {
def apply(s:String):Option[Section] = s match {
case "auto-loans" => Some(AUTO_LOANS)
case "student" => Some(STUDENT)
case _ =>None
}
}
and
sealed trait UserTypeFinder[A] {
def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User]
}
object UserTypeFinder {
def apply[A](implicit utf: UserTypeFinder[A]): UserTypeFinder[A]=utf
}
implicit val autoLoans = new UserTypeFinder[AUTO_LOANS.type] {
override def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User] = { .. }
}
def findUser[A: UserTypeFinder](section: A, fs: Set[Fact], fv: Option[FactVector]): Option[User] = {
UserTypeFinder[A].user(fs, fv)
}
now I do:
findUser(Section("auto-loans"),Set(),None) the type of Section("auto-loans") is Section not AUTO_LOANS. I'd like to preserve type for the type classes to work.
I've looked at shapeless dependent types so I was thinking of storing type Out in each case object (as seen above) then after getting the object casting it to Out:
val auto0=Section("auto-loans")
val v0=auto0.asInstanceOf[auto0.Out]
now the type of v0 is Out instead of AUTO_LOANS so this solves nothing.
Any ideas how to preserve types or how to get them at compile time? I'm not quite sure if I can use Aux for this. Any ideas?
scala type-conversion shapeless dependent-type downcasting
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
add a comment |
Here's code I have:
sealed trait Section {
val value:String
type Out
}
case object AUTO_LOANS extends Section{
val value="auto-loans"
type Out = AUTO_LOANS.type
}
case object STUDENT extends Section{
val value="student"
type Out = STUDENT.type
}
object Section {
def apply(s:String):Option[Section] = s match {
case "auto-loans" => Some(AUTO_LOANS)
case "student" => Some(STUDENT)
case _ =>None
}
}
and
sealed trait UserTypeFinder[A] {
def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User]
}
object UserTypeFinder {
def apply[A](implicit utf: UserTypeFinder[A]): UserTypeFinder[A]=utf
}
implicit val autoLoans = new UserTypeFinder[AUTO_LOANS.type] {
override def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User] = { .. }
}
def findUser[A: UserTypeFinder](section: A, fs: Set[Fact], fv: Option[FactVector]): Option[User] = {
UserTypeFinder[A].user(fs, fv)
}
now I do:
findUser(Section("auto-loans"),Set(),None) the type of Section("auto-loans") is Section not AUTO_LOANS. I'd like to preserve type for the type classes to work.
I've looked at shapeless dependent types so I was thinking of storing type Out in each case object (as seen above) then after getting the object casting it to Out:
val auto0=Section("auto-loans")
val v0=auto0.asInstanceOf[auto0.Out]
now the type of v0 is Out instead of AUTO_LOANS so this solves nothing.
Any ideas how to preserve types or how to get them at compile time? I'm not quite sure if I can use Aux for this. Any ideas?
scala type-conversion shapeless dependent-type downcasting
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
Possible duplicate of Function that retrieves element from HList (while preserving its type)
– Dmytro Mitin
Nov 20 '18 at 10:10
add a comment |
Here's code I have:
sealed trait Section {
val value:String
type Out
}
case object AUTO_LOANS extends Section{
val value="auto-loans"
type Out = AUTO_LOANS.type
}
case object STUDENT extends Section{
val value="student"
type Out = STUDENT.type
}
object Section {
def apply(s:String):Option[Section] = s match {
case "auto-loans" => Some(AUTO_LOANS)
case "student" => Some(STUDENT)
case _ =>None
}
}
and
sealed trait UserTypeFinder[A] {
def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User]
}
object UserTypeFinder {
def apply[A](implicit utf: UserTypeFinder[A]): UserTypeFinder[A]=utf
}
implicit val autoLoans = new UserTypeFinder[AUTO_LOANS.type] {
override def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User] = { .. }
}
def findUser[A: UserTypeFinder](section: A, fs: Set[Fact], fv: Option[FactVector]): Option[User] = {
UserTypeFinder[A].user(fs, fv)
}
now I do:
findUser(Section("auto-loans"),Set(),None) the type of Section("auto-loans") is Section not AUTO_LOANS. I'd like to preserve type for the type classes to work.
I've looked at shapeless dependent types so I was thinking of storing type Out in each case object (as seen above) then after getting the object casting it to Out:
val auto0=Section("auto-loans")
val v0=auto0.asInstanceOf[auto0.Out]
now the type of v0 is Out instead of AUTO_LOANS so this solves nothing.
Any ideas how to preserve types or how to get them at compile time? I'm not quite sure if I can use Aux for this. Any ideas?
scala type-conversion shapeless dependent-type downcasting
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
Here's code I have:
sealed trait Section {
val value:String
type Out
}
case object AUTO_LOANS extends Section{
val value="auto-loans"
type Out = AUTO_LOANS.type
}
case object STUDENT extends Section{
val value="student"
type Out = STUDENT.type
}
object Section {
def apply(s:String):Option[Section] = s match {
case "auto-loans" => Some(AUTO_LOANS)
case "student" => Some(STUDENT)
case _ =>None
}
}
and
sealed trait UserTypeFinder[A] {
def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User]
}
object UserTypeFinder {
def apply[A](implicit utf: UserTypeFinder[A]): UserTypeFinder[A]=utf
}
implicit val autoLoans = new UserTypeFinder[AUTO_LOANS.type] {
override def user[A](facts: Set[Fact], fv: Option[FactVector]): Option[User] = { .. }
}
def findUser[A: UserTypeFinder](section: A, fs: Set[Fact], fv: Option[FactVector]): Option[User] = {
UserTypeFinder[A].user(fs, fv)
}
now I do:
findUser(Section("auto-loans"),Set(),None) the type of Section("auto-loans") is Section not AUTO_LOANS. I'd like to preserve type for the type classes to work.
I've looked at shapeless dependent types so I was thinking of storing type Out in each case object (as seen above) then after getting the object casting it to Out:
val auto0=Section("auto-loans")
val v0=auto0.asInstanceOf[auto0.Out]
now the type of v0 is Out instead of AUTO_LOANS so this solves nothing.
Any ideas how to preserve types or how to get them at compile time? I'm not quite sure if I can use Aux for this. Any ideas?
scala type-conversion shapeless dependent-type downcasting
scala type-conversion shapeless dependent-type downcasting
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
asked Nov 19 '18 at 21:30
AdrianAdrian
3,89073970
3,89073970
Possible duplicate of Function that retrieves element from HList (while preserving its type)
– Dmytro Mitin
Nov 20 '18 at 10:10
add a comment |
Possible duplicate of Function that retrieves element from HList (while preserving its type)
– Dmytro Mitin
Nov 20 '18 at 10:10
Possible duplicate of Function that retrieves element from HList (while preserving its type)
– Dmytro Mitin
Nov 20 '18 at 10:10
Possible duplicate of Function that retrieves element from HList (while preserving its type)
– Dmytro Mitin
Nov 20 '18 at 10:10
add a comment |
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Possible duplicate of Function that retrieves element from HList (while preserving its type)
– Dmytro Mitin
Nov 20 '18 at 10:10