Update to new combinators

Author: phischu

examples/stdlib/stream/first.check

@@ -1,3 +1,3 @@
 1
 true
-MissingValue: code in first did not emit any values
+MissingValue

examples/stdlib/stream/first.effekt

@@ -1,24 +1,12 @@
-def printResult[T](result: Result[T, MissingValue]) { printSuccess: T => Unit } = result match {
-  case Success(value) => printSuccess(value)
-  case Error(err, msg) => println("MissingValue: " ++ msg)
+def printOption[T](option: Option[T]) { printSuccess: T => Unit } = option match {
+  case Some(value) => printSuccess(value)
+  case None() => println("MissingValue")
 }
 
 def main() = {
-  printResult(
-    on[MissingValue].result {
-      stream::first[Int] { [1, 2, 3].each }
-    }
-  ) { x => println(x) }
+  printOption(optionally { stream::first[Int] { [1, 2, 3].each } }) { x => println(x) }
 
-  printResult(
-    on[MissingValue].result {
-      first[Bool] { do emit(true) }
-    }
-  ) { x => println(x) }
+  printOption(optionally { first[Bool] { do emit(true) } })  { x => println(x) }
 
-  printResult(
-    on[MissingValue].result {
-      first[String] { () } // empty stream
-    }
-  ) { x => println(x) }
+  printOption(optionally { first[String] { () } })  { x => println(x) }
 }

libraries/common/stream.effekt

@@ -339,14 +339,14 @@ def tee[A]{ cons1: { => Unit / emit[A] } => Unit }{ cons2: { => Unit / emit[A] }
 /// > first[Bool] { do emit(true) }
 /// true
 /// > first[String] { () } // empty stream
-/// <Exception MissingValue: code in first did not emit any values>
+/// <fail>
 /// ```
-def first[A] { body: => Unit / emit[A] }: A / Exception[MissingValue] =
+def first[A] { stream: () => Unit / emit[A] }: A / fail = {
   try {
+    def body(): A = { stream(); do fail() }
     body()
-    val r: A = do raise[MissingValue](MissingValue(), "code in first did not emit any values")
-    r
   } with emit[A] { a => a }
+}
 
 namespace returning {