Update demos and adds <|

demos/interactionTrees/writeThenRead.tri

@@ -0,0 +1,20 @@
+!import "../../lib/base.tri" !Local
+!import "../../lib/list.tri" !Local
+!import "../../lib/io.tri"   !Local
+
+-- Write a file, then read it back.
+--   thenIO discards the writeFile Result and continues.
+--   Run with --unsafe-io (needs both read and write permissions).
+
+writeThenRead = (path text :
+  thenIO
+    (writeFile path text)
+    (readFile path))
+
+main = io <|
+  (bind (writeThenRead "/tmp/tricu-demo.txt" "hello from tricu")
+    (result :
+      matchResult
+        (err rest : putStrLn "error")
+        (contents rest : putStrLn contents)
+        result))