Refactor 'stream', add a few examples

examples/stdlib/stream/fibonacci.check

@@ -0,0 +1,2 @@
+The first 10 Fibonacci numbers:
+Cons(0, Cons(1, Cons(1, Cons(2, Cons(3, Cons(5, Cons(8, Cons(13, Cons(21, Cons(34, Nil()))))))))))

examples/stdlib/stream/fibonacci.effekt

@@ -0,0 +1,20 @@
+import stream
+
+def main() = {
+  val max = 10
+
+  val fibs = collectList[Int] {
+    var a = 0
+    var b = 1
+
+    replicate(max) {
+      val current = a
+      val next = a + b
+      a = b
+      b = next
+      current
+    }
+  }
+  println("The first " ++ show(max) ++ " Fibonacci numbers:")
+  println(fibs)
+}

examples/stdlib/stream/neighbours.check

@@ -0,0 +1,35 @@
+The immediate neighbours of [4, 3] are:
+[3, 2]
+[3, 3]
+[3, 4]
+[4, 2]
+[4, 4]
+[5, 2]
+[5, 3]
+[5, 4]
+
+The neighbours and their neighbours of [4, 3] are:
+[2, 1]
+[2, 2]
+[2, 3]
+[2, 4]
+[2, 5]
+[3, 1]
+[3, 2]
+[3, 3]
+[3, 4]
+[3, 5]
+[4, 1]
+[4, 2]
+[4, 4]
+[4, 5]
+[5, 1]
+[5, 2]
+[5, 3]
+[5, 4]
+[5, 5]
+[6, 1]
+[6, 2]
+[6, 3]
+[6, 4]
+[6, 5]

examples/stdlib/stream/neighbours.effekt

@@ -0,0 +1,38 @@
+import stream
+
+record Pos(x: Int, y: Int)
+
+def equals(left: Pos, right: Pos) = (left, right) match {
+  case (Pos(lx, ly), Pos(rx, ry)) => lx == rx && ly == ry
+}
+
+def show(p: Pos) = "[" ++ show(p.x) ++ ", " ++ show(p.y) ++ "]"
+
+/// Gets the neighbours of a given position.
+/// with radius=1, those are immediate neighbours (including the diagonal)
+/// with radius=2, these are neighbours&their neighbours
+/// ...
+def neighboursOf(pos: Pos, radius: Int) = {
+  with val dx = for[Int] { range(neg(radius), radius + 1) }
+  with val dy = for[Int] { range(neg(radius), radius + 1) }
+  val newPosition = Pos(pos.x + dx, pos.y + dy)
+  do emit(newPosition)
+}
+
+def main() = {
+  val start = Pos(4, 3)
+
+  println("The immediate neighbours of " ++ show(start) ++ " are:")
+  for[Pos] { start.neighboursOf(1) } { 
+    case p and not(p.equals(start)) => println(show(p))
+    case _ => ()
+  }
+
+  println("")
+
+  println("The neighbours and their neighbours of " ++ show(start) ++ " are:")
+  for[Pos] { start.neighboursOf(2) } { 
+    case p and not(p.equals(start)) => println(show(p))
+    case _ => ()
+  }
+}

examples/stdlib/stream/sum_of_squares.check

@@ -0,0 +1,2 @@
+The sum of squares from 1 to 10 is:
+385

examples/stdlib/stream/sum_of_squares.effekt

@@ -0,0 +1,12 @@
+import stream
+
+def squares(max: Int): Unit / emit[Int] = {
+  with val n = for[Int] { range(1, max) }
+  do emit(n * n)
+}
+
+def main() = {
+  val max = 10
+  println("The sum of squares from 1 to " ++ show(max) ++ " is:")
+  println(sum { squares(max + 1) })
+}