Update demos and adds <|

demos/interactionTrees/shout.tri

@@ -0,0 +1,23 @@
+!import "../../lib/base.tri" !Local
+!import "../../lib/list.tri" !Local
+!import "../../lib/io.tri"   !Local
+
+-- Transform an IO result.
+--   mapIO applies a pure function to the value produced by an action.
+--   Run with --allow-read PATH or --unsafe-io.
+
+safeRead = (path :
+  bind (readFile path)
+    (result :
+      matchResult
+        (err rest : pure "missing")
+        (contents rest : pure contents)
+        result))
+
+shout = (path :
+  mapIO (safeRead path)
+    (text : append text "!!!"))
+
+main = io (bind 
+    (shout "demos/interactionTrees/greet.tri")
+    (text : putStrLn text))