4107

Return other values along with the current continuation.

1 files changed, 39 insertions, 0 deletions

diff --git a/continuation4.mu b/continuation4.mu
new file mode 100644
index 00000000..5957c1be
--- /dev/null
+++ b/continuation4.mu
@@ -0,0 +1,39 @@
+# example program showing 'return-continuation-until-mark' return other values
+# alongside continuations
+
+def main [
+  local-scope
+  l:&:list:num <- copy 0
+  l <- push 3, l
+  l <- push 2, l
+  l <- push 1, l
+  k:continuation, x:num, done?:bool <- call-with-continuation-mark create-yielder, l
+  {
+    break-if done?
+    $print x 10/newline
+    k, x:num, done?:bool <- call k
+    loop
+  }
+]
+
+def create-yielder l:&:list:num -> n:num, done?:bool [
+  local-scope
+  load-ingredients
+  {
+    done? <- equal l, 0
+    # Our current primitives can lead to gnarly code to ensure that we always
+    # statically match a continuation call with a 'return-continuation-until-mark'.
+    # Try to design functions to either always return or always return continuation.
+    {
+      # should we have conditional versions of return-continuation-until-mark
+      # analogous to return-if and return-unless? Names get really long.
+      break-unless done?
+      return-continuation-until-mark 0, done?
+      return 0, done?  # just a guard rail; should never execute
+    }
+    n <- first l
+    l <- rest l
+    return-continuation-until-mark n, done?
+    loop
+  }
+]