Add passing tests

1 files changed, 175 insertions, 0 deletions

diff --git a/tests/pos/tcpoly_seq.scala b/tests/pos/tcpoly_seq.scala
new file mode 100644
index 000000000..e8711d1c4
--- /dev/null
+++ b/tests/pos/tcpoly_seq.scala
@@ -0,0 +1,175 @@
+package examples.tcpoly.collection;
+
+trait HOSeq {
+  // an internal interface that encapsulates the accumulation of elements (of type elT) to produce
+  // a structure of type coll[elT] -- different kinds of collections should provide different implicit
+  // values implementing this interface, in order to provide more performant ways of building that structure
+  trait Accumulator[+coll[x], elT] {
+    def += (el: elT): Unit
+    def result: coll[elT]
+  }
+
+
+  // Iterable abstracts over the type of its structure as well as its elements (see PolyP's Bifunctor)
+  // m[x] is intentionally unbounded: fold can then be defined nicely
+  // variance: if we write m[+x] instead of +m[+x], x is an invariant position because its enclosing type
+  //           is an invariant position -- should probably rule that out?
+  trait Iterable[+m[+x], +t] {
+    //def unit[a](orig: a): m[a]
+    def iterator: Iterator[t]
+
+    // construct an empty accumulator that will produce the same structure as this iterable, with elements of type t
+    def accumulator[t]: Accumulator[m, t]
+
+    def filter(p: t => Boolean): m[t] = {
+      val buf = accumulator[t]
+      val elems = iterator
+      while (elems.hasNext) { val x = elems.next; if (p(x)) buf += x }
+      buf.result
+    }
+
+    def map[s](f: t => s): m[s] = {
+      val buf = accumulator[s]
+      val elems = iterator
+      while (elems.hasNext) buf += f(elems.next)
+      buf.result
+    }
+
+    // flatMap is a more specialized map, it only works if the mapped function produces Iterable values,
+    // which are then added to the result one by one
+    // the compiler should be able to find the right accumulator (implicit buf) to build the result
+    // to get concat, resColl = SingletonIterable, f = unit for SingletonIterable
+    def flatMap[resColl[+x] <: Iterable[resColl, x], s](f: t => resColl[s])(implicit buf: Accumulator[resColl, s]): resColl[s] = {
+        // TODO:  would a viewbound for resColl[x] be better?
+        // -- 2nd-order type params are not yet in scope in view bound
+      val elems = iterator
+      while (elems.hasNext) {
+        val elemss: Iterator[s] = f(elems.next).iterator
+        while (elemss.hasNext) buf += elemss.next
+      }
+      buf.result
+    }
+  }
+
+  final class ListBuffer[A] {
+    private var start: List[A] = Nil
+    private var last: ::[A] = _
+    private var exported: Boolean = false
+
+    /** Appends a single element to this buffer.
+     *
+     *  @param x  the element to append.
+     */
+    def += (x: A): Unit = {
+      if (exported) copy
+      if (start.isEmpty) {
+        last = new HOSeq.this.:: (x, Nil)
+        start = last
+      } else {
+        val last1 = last
+        last = new HOSeq.this.:: (x, null) // hack: ::'s tail will actually be last
+        //last1.tl = last
+      }
+    }
+
+    /** Converts this buffer to a list
+     */
+    def toList: List[A] = {
+      exported = !start.isEmpty
+      start
+    }
+
+    /** Clears the buffer contents.
+     */
+    def clear: Unit = {
+      start = Nil
+      exported = false
+    }
+
+    /** Copy contents of this buffer */
+    private def copy: Unit = {
+      var cursor = start
+      val limit = last.tail
+      clear
+      while (cursor ne limit) {
+        this += cursor.head
+        cursor = cursor.tail
+      }
+    }
+  }
+
+  implicit def listAccumulator[elT]: Accumulator[List, elT] = new Accumulator[List, elT] {
+    private[this] val buff = new ListBuffer[elT]
+    def += (el: elT): Unit = buff += el
+    def result: List[elT] = buff.toList
+  }
+
+  trait List[+t] extends Iterable[List, t] {
+    def head: t
+    def tail: List[t]
+    def isEmpty: Boolean
+    def iterator: Iterator[t] = new Iterator[t] {
+    var these = List.this
+    def hasNext: Boolean = !these.isEmpty
+    def next: t =
+      if (!hasNext)
+        throw new NoSuchElementException("next on empty Iterator")
+      else {
+        val result = these.head; these = these.tail; result
+      }
+    }
+    // construct an empty accumulator that will produce the same structure as this iterable, with elements of type t
+    def accumulator[t]: Accumulator[List, t] = listAccumulator[t]
+  }
+
+  // TODO: the var tl approach does not seem to work because subtyping isn't fully working yet
+  final case class ::[+b](hd: b, private val tl: List[b]) extends List[b] {
+    def head = hd
+    def tail = if (tl==null) this else tl // hack
+    override def isEmpty: Boolean = false
+  }
+
+  case object Nil extends List[Nothing] {
+    def isEmpty = true
+    def head: Nothing =
+      throw new NoSuchElementException("head of empty list")
+    def tail: List[Nothing] =
+      throw new NoSuchElementException("tail of empty list")
+  }
+}
+
+
+
+// misc signatures collected from mailing list / library code:
+    /*override def flatMap[B](f: A => Iterable[B]): Set[B]
+    final override def flatMap[b](f: Any => Iterable[b]): Array[b]
+     def flatMap[b](f: a => Parser[b]) = new Parser[b]
+     override def flatMap[b](f: a => Iterable[b]): List[b]
+
+
+    MapResult[K] <: Seq[K]
+    FilterResult <: Seq[T]
+    Concat <: Seq[T]
+    Subseq <: Seq[T]
+
+
+    def map[K](f: T=>K): MapResult[K]
+    def filter(f: T=>Boolean): FilterResult
+    def subseq(from: Int, to: Int): Subseq
+    def flatMap[S <: Seq[K], K](f: T => S): S#Concat  // legal?
+    def concat(others: Seq[T]): Concat
+     */
+
+/*trait Iterator[t] {
+  // @post hasAdvanced implies hasNext
+  // model def hasAdvanced: Boolean
+
+  def hasNext: Boolean // pure
+
+  // @pre hasAdvanced
+  def current: t       // pure
+
+  // @pre hasNext
+  // @post hasAdvanced
+  def advance: Unit
+}*/