added __init__ type function for creating messages.

src/nima.nim

@@ -3,10 +3,16 @@
 # but you can remove it if you wish.
 
 type
-  Sender = int
-  Receiver = int
-  Topic = string
-  Message* = tuple[sender:Sender, receiver:Receiver, topic:Topic]
+  Message* = object
+    sender*: int
+    receiver*: int
+    topic*: string
+
+
+proc newMessage*(sender,receiver:int, topic:string): Message = 
+  result.sender = sender
+  result.receiver = receiver
+  result.topic = topic
 
 
 proc copy*(self: Message): Message = 

tests/test1.nim

@@ -10,12 +10,12 @@ import unittest
 import nima
 
 test "can create message":
-  var msg: Message = (sender:1, receiver:2, topic:"hello")
+  var msg = newMessage(sender=1, receiver=2, topic="hello")
   check msg.sender == 1
   check msg.receiver == 2
   check msg.topic == "hello"
-  msg_copy = msg.copy()
-
+  var msg2 = msg.copy()
+  check msg == msg2
 
 test "can create agent":
   var agent = newAgent()
@@ -26,4 +26,5 @@ test "minimal system":
   var s = newScheduler()
   s.add(agent)
   s.run()
-  check s.t == 1
+  check s.t == 1
+