Hylolib: Switch to member based type classes

Author: odersky

tests/pos/hylolib/AnyCollection.scala

@@ -19,7 +19,7 @@ object AnyCollection {
     // and `anyValueIsValue` when the method is called on a collection of `Int`s. None of these
     // choices is even correct! Note also that the ambiguity is suppressed if the constructor of
     // `AnyValue` is declared with a context bound rather than an implicit parameter.
-    given Value[b.Position] = b.positionIsValue
+    given b.Position is Value = b.positionIsValue
 
     def start(): AnyValue =
       AnyValue(base.startPosition)
@@ -42,7 +42,7 @@ object AnyCollection {
 
 }
 
-given anyCollectionIsCollection[T: Value]: Collection[AnyCollection[T]] with {
+given [T: Value] => AnyCollection[T] is Collection with {
 
   type Element = T
   type Position = AnyValue

tests/pos/hylolib/AnyValue.scala

@@ -58,9 +58,9 @@ object AnyValue {
 
 }
 
-given anyValueIsValue: Value[AnyValue] with {
+given AnyValue is Value:
 
-  extension (self: AnyValue) {
+  extension (self: AnyValue)
 
     def copy(): AnyValue =
       self.copy()
@@ -71,6 +71,3 @@ given anyValueIsValue: Value[AnyValue] with {
     def hashInto(hasher: Hasher): Hasher =
       self.hashInto(hasher)
 
-  }
-
-}

tests/pos/hylolib/BitArray.scala

@@ -318,7 +318,7 @@ object BitArray {
 
 }
 
-given bitArrayPositionIsValue: Value[BitArray.Position] with {
+given BitArray.Position is Value with {
 
   extension (self: BitArray.Position) {
 
@@ -335,7 +335,7 @@ given bitArrayPositionIsValue: Value[BitArray.Position] with {
 
 }
 
-given bitArrayIsCollection: Collection[BitArray] with {
+given BitArray is Collection with {
 
   type Element = Boolean
   type Position = BitArray.Position

tests/pos/hylolib/Collection.scala

@@ -2,7 +2,8 @@
 package hylo
 
 /** A collection of elements accessible by their position. */
-trait Collection[Self] {
+trait Collection {
+  type Self
 
   /** The type of the elements in the collection. */
   type Element: Value
@@ -213,7 +214,7 @@ extension [Self: Collection as s](self: Self) {
     * @complexity
     *   O(n) where n is the number of elements in `self`.
     */
-  def minElement()(using Comparable[s.Element]): Option[s.Element] =
+  def minElement()(using s.Element is Comparable): Option[s.Element] =
     self.minElement(isLessThan = _ `lt` _)
 
   /** Returns the maximum element in `self`, using `isGreaterThan` to compare elements.
@@ -229,7 +230,7 @@ extension [Self: Collection as s](self: Self) {
     * @complexity
     *   O(n) where n is the number of elements in `self`.
     */
-  def maxElement()(using Comparable[s.Element]): Option[s.Element] =
+  def maxElement()(using s.Element is Comparable): Option[s.Element] =
     self.maxElement(isGreaterThan = _ `gt` _)
 
   /** Returns the maximum element in `self`, using `isOrderedBefore` to compare elements.
@@ -257,12 +258,12 @@ extension [Self: Collection as s](self: Self) {
 
 }
 
-extension [Self: Collection as s](self: Self)(using
-    Value[s.Element]
+extension [Self: Collection as s](self: Self)(
+    using s.Element is Value
 ) {
 
   /** Returns `true` if `self` contains the same elements as `other`, in the same order. */
-  def elementsEqual[T](using o: Collection[T] { type Element = s.Element })(other: T): Boolean =
+  def elementsEqual[T](using o: T is Collection { type Element = s.Element })(other: T): Boolean =
     def loop(i: s.Position, j: o.Position): Boolean =
       if (i `eq` self.endPosition) {
         j `eq` other.endPosition

tests/pos/hylolib/CoreTraits.scala

@@ -5,7 +5,8 @@ package hylo
   * The data structure of and algorithms of Hylo's standard library operate "notional values" rather
   * than arbitrary references. This trait defines the basis operations of all values.
   */
-trait Value[Self] {
+trait Value:
+  type Self
 
   extension (self: Self) {
 
@@ -15,20 +16,18 @@ trait Value[Self] {
     /** Returns `true` iff `self` and `other` have an equivalent value. */
     def eq(other: Self): Boolean
 
+    def neq(other: Self): Boolean = !self.eq(other)
+
     /** Hashes the salient parts of `self` into `hasher`. */
     def hashInto(hasher: Hasher): Hasher
 
   }
 
-}
-
-extension [Self: Value](self: Self) def neq(other: Self): Boolean = !self.eq(other)
-
 // ----------------------------------------------------------------------------
 // Comparable
 // ----------------------------------------------------------------------------
 
-trait Comparable[Self] extends Value[Self] {
+trait Comparable extends Value {
 
   extension (self: Self) {
 

tests/pos/hylolib/HyArray.scala

@@ -161,7 +161,7 @@ object HyArray {
 
 }
 
-given [T: Value] => Value[HyArray[T]] with {
+given [T: Value] => HyArray[T] is Value with {
 
   extension (self: HyArray[T]) {
 
@@ -178,7 +178,7 @@ given [T: Value] => Value[HyArray[T]] with {
 
 }
 
-given [T: Value] => Collection[HyArray[T]] with {
+given [T: Value] => HyArray[T] is Collection with {
 
   type Element = T
   type Position = Int

tests/pos/hylolib/Integers.scala

@@ -1,6 +1,6 @@
 package hylo
 
-given booleanIsValue: Value[Boolean] with {
+given Boolean is Value with {
 
   extension (self: Boolean) {
 
@@ -18,7 +18,7 @@ given booleanIsValue: Value[Boolean] with {
 
 }
 
-given intIsValue: Value[Int] with {
+given Int is Value with {
 
   extension (self: Int) {
 
@@ -36,7 +36,7 @@ given intIsValue: Value[Int] with {
 
 }
 
-given intIsComparable: Comparable[Int] with {
+given Int is Comparable with {
 
   extension (self: Int) {
 

tests/pos/hylolib/Slice.scala

@@ -24,7 +24,7 @@ final class Slice[Base: Collection as b](
 
 }
 
-given sliceIsCollection[T: Collection as c]: Collection[Slice[T]] with {
+given [T: Collection as c] => Slice[T] is Collection with {
 
   type Element = c.Element
   type Position = c.Position