Writing a generic Scala merge function, can't get types to line up for compilerCreating an empty IndexedSeq of a sub-type and using TailRecHow to get the type of T from a member of a generic class or method?How do I get around type erasure on Scala? Or, why can't I get the type parameter of my collections?Scala: Abstract types vs genericsGet generic type of class at runtimeHow to get a class instance of generics type TGeneric type inference in ScalaScala: conforming concrete type to generics with boundsScala generic type parameters issuesScala Generics Type Bounds - Pointing to the Actual TypeScala can't convert Java map keySet to a Sequence type
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Writing a generic Scala merge function, can't get types to line up for compiler
Creating an empty IndexedSeq of a sub-type and using TailRecHow to get the type of T from a member of a generic class or method?How do I get around type erasure on Scala? Or, why can't I get the type parameter of my collections?Scala: Abstract types vs genericsGet generic type of class at runtimeHow to get a class instance of generics type TGeneric type inference in ScalaScala: conforming concrete type to generics with boundsScala generic type parameters issuesScala Generics Type Bounds - Pointing to the Actual TypeScala can't convert Java map keySet to a Sequence type
I'm trying to learn FP with Scala. I've got a function on an object to merge two sorted collections and return the same type. It looks like this:
@tailrec def merge[A, Repr <: Seq[A]](merged: Repr, l1: Repr, l2: Repr)(
implicit ordering: Ordering[A]): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
It's giving me the compiler error "Expression of type Seq[A] doesn't conform to the expected type Repr
scala generics
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
add a comment |
I'm trying to learn FP with Scala. I've got a function on an object to merge two sorted collections and return the same type. It looks like this:
@tailrec def merge[A, Repr <: Seq[A]](merged: Repr, l1: Repr, l2: Repr)(
implicit ordering: Ordering[A]): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
It's giving me the compiler error "Expression of type Seq[A] doesn't conform to the expected type Repr
scala generics
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
add a comment |
I'm trying to learn FP with Scala. I've got a function on an object to merge two sorted collections and return the same type. It looks like this:
@tailrec def merge[A, Repr <: Seq[A]](merged: Repr, l1: Repr, l2: Repr)(
implicit ordering: Ordering[A]): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
It's giving me the compiler error "Expression of type Seq[A] doesn't conform to the expected type Repr
scala generics
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
I'm trying to learn FP with Scala. I've got a function on an object to merge two sorted collections and return the same type. It looks like this:
@tailrec def merge[A, Repr <: Seq[A]](merged: Repr, l1: Repr, l2: Repr)(
implicit ordering: Ordering[A]): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
It's giving me the compiler error "Expression of type Seq[A] doesn't conform to the expected type Repr
scala generics
scala generics
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
edited Mar 25 at 17:29
Yuval Itzchakov
119k26 gold badges182 silver badges250 bronze badges
119k26 gold badges182 silver badges250 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
asked Mar 25 at 17:23
Jason CarreiraJason Carreira
12311 bronze badges
12311 bronze badges
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
Try
@tailrec def merge[A, Repr](merged: Repr, l1: Repr, l2: Repr)(implicit
ev: Repr => SeqLike[A, Repr],
cbf: CanBuildFrom[Repr, A, Repr],
ordering: Ordering[A]
): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
add a comment |
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
Try
@tailrec def merge[A, Repr](merged: Repr, l1: Repr, l2: Repr)(implicit
ev: Repr => SeqLike[A, Repr],
cbf: CanBuildFrom[Repr, A, Repr],
ordering: Ordering[A]
): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
add a comment |
Try
@tailrec def merge[A, Repr](merged: Repr, l1: Repr, l2: Repr)(implicit
ev: Repr => SeqLike[A, Repr],
cbf: CanBuildFrom[Repr, A, Repr],
ordering: Ordering[A]
): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
add a comment |
Try
@tailrec def merge[A, Repr](merged: Repr, l1: Repr, l2: Repr)(implicit
ev: Repr => SeqLike[A, Repr],
cbf: CanBuildFrom[Repr, A, Repr],
ordering: Ordering[A]
): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
Try
@tailrec def merge[A, Repr](merged: Repr, l1: Repr, l2: Repr)(implicit
ev: Repr => SeqLike[A, Repr],
cbf: CanBuildFrom[Repr, A, Repr],
ordering: Ordering[A]
): Repr =
if (l1.isEmpty) merged ++ l2
else if (l2.isEmpty) merged ++ l1
else
val l1Head: A = l1.head
val l2Head = l2.head
val orderVal = ordering.compare(l1Head, l2Head)
if (orderVal <= 0)
val m2: Repr = l1Head +: merged
merge[A, Repr](m2, l1.tail, l2)
else
merge[A, Repr](l2Head +: merged, l1, l2.tail)
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
answered Mar 25 at 18:55
Dmytro MitinDmytro Mitin
12.6k1 gold badge7 silver badges22 bronze badges
12.6k1 gold badge7 silver badges22 bronze badges
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
add a comment |
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
That works! Unfortunately now that I can test my code it doesn't do the right thing... but at least now I can test it!
– Jason Carreira
Mar 25 at 19:18
add a comment |
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