Update demos and adds <|

demos/interactionTrees/yield.tri

@@ -0,0 +1,33 @@
+!import "../../lib/base.tri" !Local
+!import "../../lib/list.tri" !Local
+!import "../../lib/io.tri"   !Local
+
+-- Cooperative scheduling with yield.
+--   yield returns control to the scheduler so other tasks can run.
+--
+--   Two tasks print alternately because each yields after every line.
+
+--chatter = (name n :
+--  bind (putStrLn (append name " says 1")) (_ :
+--  bind yield (_ :
+--  bind (putStrLn (append name " says 2")) (_ :
+--  bind yield (_ :
+--  bind (putStrLn (append name " says 3")) (_ :
+--  pure n))))))
+
+chatter = name n : bind <|
+  putStrLn (append name " says 1") (_ :
+  bind yield (_ :
+  bind (putStrLn (append name " says 2")) (_ :
+  bind yield (_ :
+  bind (putStrLn (append name " says 3")) (_ :
+  pure n)))))
+
+
+main = io <|
+  bind (fork (chatter "A" "doneA")) (ha :
+  bind (fork (chatter "B" "doneB")) (hb :
+  bind yield (_ :
+  bind (await ha) (a :
+  bind (await hb) (b :
+  putStrLn (append "Finished: " (append a (append " " b))))))))