From c6e22028de6206ac68508c3717ef42226253b046 Mon Sep 17 00:00:00 2001
From: Philipp Schuster <philipp.schuster@uni-tuebingen.de>
Date: Mon, 25 Nov 2024 13:50:59 +0100
Subject: [PATCH] Add example of pull streams

---
 .../src/test/scala/effekt/StdlibTests.scala   |  4 ++-
 examples/stdlib/stream/fuse_newlines.check    |  3 ++
 examples/stdlib/stream/fuse_newlines.effekt   | 32 +++++++++++++++++++
 libraries/common/stream.effekt                |  1 +
 4 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 examples/stdlib/stream/fuse_newlines.check
 create mode 100644 examples/stdlib/stream/fuse_newlines.effekt

diff --git a/effekt/jvm/src/test/scala/effekt/StdlibTests.scala b/effekt/jvm/src/test/scala/effekt/StdlibTests.scala
index 451cf9c5b..f74cb0e21 100644
--- a/effekt/jvm/src/test/scala/effekt/StdlibTests.scala
+++ b/effekt/jvm/src/test/scala/effekt/StdlibTests.scala
@@ -24,7 +24,8 @@ abstract class StdlibChezTests extends StdlibTests {
     // Not implemented yet
     examplesDir / "stdlib" / "bytearray",
     examplesDir / "stdlib" / "io",
-    examplesDir / "stdlib" / "stream" / "characters.effekt"
+    examplesDir / "stdlib" / "stream" / "characters.effekt",
+    examplesDir / "stdlib" / "stream" / "fuse_newlines.effekt"
   )
 }
 class StdlibChezSchemeMonadicTests extends StdlibChezTests {
@@ -46,6 +47,7 @@ class StdlibLLVMTests extends StdlibTests {
     // Valgrind leak/failure
     examplesDir / "stdlib" / "bytearray" / "bytearray.effekt",
     examplesDir / "stdlib" / "stream" / "characters.effekt",
+    examplesDir / "stdlib" / "stream" / "fuse_newlines.effekt",
     examplesDir / "stdlib" / "io" / "filesystem" / "async_file_io.effekt",
     examplesDir / "stdlib" / "io" / "filesystem" / "files.effekt",
     examplesDir / "stdlib" / "io" / "filesystem" / "wordcount.effekt",
diff --git a/examples/stdlib/stream/fuse_newlines.check b/examples/stdlib/stream/fuse_newlines.check
new file mode 100644
index 000000000..252ac0b51
--- /dev/null
+++ b/examples/stdlib/stream/fuse_newlines.check
@@ -0,0 +1,3 @@
+ab
+c
+de
\ No newline at end of file
diff --git a/examples/stdlib/stream/fuse_newlines.effekt b/examples/stdlib/stream/fuse_newlines.effekt
new file mode 100644
index 000000000..3c050c347
--- /dev/null
+++ b/examples/stdlib/stream/fuse_newlines.effekt
@@ -0,0 +1,32 @@
+import stream
+
+def fuseNewlines(): Nothing / {read[Char], emit[Char], stop} = {
+  val c = do read[Char]()
+  if (c == '\n') {
+    do emit(c)
+    skipNewlines()
+  } else {
+    do emit(c)
+    fuseNewlines()
+  }
+}
+
+def skipNewlines(): Nothing / {read[Char], emit[Char], stop} = {
+  val c = do read[Char]()
+  if (c == '\n') {
+    skipNewlines()
+  } else {
+    do emit(c)
+    fuseNewlines()
+  }
+}
+
+def main() = {
+  with feed("ab\n\nc\nde")
+  println(collectString {
+    with exhaustively
+    fuseNewlines()
+  })
+}
+
+
diff --git a/libraries/common/stream.effekt b/libraries/common/stream.effekt
index 9fd79dec0..6337c1f1c 100644
--- a/libraries/common/stream.effekt
+++ b/libraries/common/stream.effekt
@@ -93,6 +93,7 @@ def boundary { program: () => Any / stop }: Unit = {
   ()
 }
 
+/// Run `program` forever until `stop` is thrown.
 def exhaustively { program: () => Any / stop }: Unit =
   try {
     def go(): Unit = {