Helpful library updates

demos/interactionTrees/echo-server.tri

@@ -2,45 +2,27 @@
 !import "../../lib/io.tri"     !Local
 !import "../../lib/socket.tri" !Local
 
--- Preserve the host-driver Result shape on error, run okCase on success.
-onOk = action okCase :
-  bind action (result :
-    matchResult
-      (err rest : pure result)
-      okCase
-      result)
-
--- Convenience: print a string and continue.
-printLn = s : bind (putStr (append s "\n")) (_ : pure t)
-
--- Main accept+echo loop. Recursion via y.
-echoLoop = y (self server :
-  bind (accept server) (acceptResult :
-    matchResult
-      (err rest :
-        bind (printLn (append "accept error: " err)) (_ :
-          self server))
-      (accepted rest :
-        matchPair
-          (clientSock addr :
-            bind (printLn (append "client from " addr)) (_ :
-              bind (recv clientSock 4096) (msgResult :
-                matchResult
-                  (err rest :
-                    bind (closeSocket clientSock) (_ :
-                      self server))
-                  (msg rest :
-                    bind (send clientSock msg) (_ :
-                      bind (closeSocket clientSock) (_ :
-                        self server)))
-                  msgResult)))
-          accepted)
-      acceptResult))
+-- Main accept+echo loop.  Recursion via y.
+echoLoop = y (self : server :
+  withAccepted_ server
+    (err :
+      bind (putStrLn (append "accept error: " err)) (_ :
+        self server))
+    (clientSock addr :
+      bind (putStrLn (append "client from " addr)) (_ :
+        onResult_ (recv clientSock 4096)
+          (err :
+            bind (closeSocket clientSock) (_ :
+              self server))
+          (msg :
+            bind (send clientSock msg) (_ :
+              bind (closeSocket clientSock) (_ :
+                self server))))))
 
 main = io (
-  onOk socket (server rest :
-    onOk (bindSocket server "127.0.0.1" 0) (_ rest :
-      onOk (listen server 5) (_ rest :
-        onOk (getSocketName server) (port rest :
-          bind (printLn (append "Echo server listening on port " (showNumber port))) (_ :
+  onOk_ socket (server :
+    onOk_ (bindSocket server "127.0.0.1" 0) (_ :
+      onOk_ (listen server 5) (_ :
+        onOk_ (getSocketName server) (port :
+          bind (putStrLn (append "Echo server listening on port " (showNumber port))) (_ :
             echoLoop server))))))