dummy threads in agents

python/hyperon/atoms.py

@@ -311,6 +311,35 @@ class MettaError(Exception):
        , but we don't want to output Python error stack."""
     pass
 
+def unwrap_args(atoms):
+    args = []
+    kwargs = {}
+    for a in atoms:
+        if isinstance(a, ExpressionAtom):
+            ch = a.get_children()
+            if len(ch) > 0 and repr(ch[0]) == "Kwargs":
+                for c in ch[1:]:
+                    try:
+                        kwarg = c.get_children()
+                        assert len(kwarg) == 2
+                    except:
+                        raise RuntimeError(f"Incorrect kwarg format {kwarg}")
+                    try:
+                        kwargs[get_string_value(kwarg[0])] = kwarg[1].get_object().content
+                    except:
+                        raise NoReduceError()
+                continue
+        try:
+            args.append(a.get_object().content)
+        except:
+            # NOTE:
+            # Currently, applying grounded operations to pure atoms is not reduced.
+            # If we want, we can raise an exception, or form an error expression instead,
+            # so a MeTTa program can catch and analyze it.
+            # raise RuntimeError("Grounded operation " + self.name + " with unwrap=True expects only grounded arguments")
+            raise NoReduceError()
+    return args, kwargs
+
 class OperationObject(GroundedObject):
     """
     An OperationObject represents an operation as a grounded object, allowing for more
@@ -385,32 +414,7 @@ def execute(self, *atoms, res_typ=AtomType.UNDEFINED):
         """
         # type-check?
         if self.unwrap:
-            args = []
-            kwargs = {}
-            for a in atoms:
-                if isinstance(a, ExpressionAtom):
-                    ch = a.get_children()
-                    if len(ch) > 0 and repr(ch[0]) == "Kwargs":
-                        for c in ch[1:]:
-                            try:
-                                kwarg = c.get_children()
-                                assert len(kwarg) == 2
-                            except:
-                                raise RuntimeError(f"Incorrect kwarg format {kwarg}")
-                            try:
-                                kwargs[get_string_value(kwarg[0])] = kwarg[1].get_object().content
-                            except:
-                                raise NoReduceError()
-                        continue
-                try:
-                    args.append(a.get_object().content)
-                except:
-                    # NOTE:
-                    # Currently, applying grounded operations to pure atoms is not reduced.
-                    # If we want, we can raise an exception, or form an error expression instead,
-                    # so a MeTTa program can catch and analyze it.
-                    # raise RuntimeError("Grounded operation " + self.name + " with unwrap=True expects only grounded arguments")
-                    raise NoReduceError()
+            args, kwargs = unwrap_args(atoms)
             try:
                 result = self.op(*args, **kwargs)
             except MettaError as e:
@@ -422,7 +426,9 @@ def execute(self, *atoms, res_typ=AtomType.UNDEFINED):
             return [ValueAtom(result, res_typ)]
         else:
             result = self.op(*atoms)
-            if not isinstance(result, list):
+            try:
+                iter(result)
+            except TypeError:
                 raise RuntimeError("Grounded operation `" + self.name + "` should return list")
             return result
 

python/hyperon/exts/agents/agent_base.py

@@ -4,8 +4,42 @@
 '''
 This is very preliminary and incomplete PoC version.
 However, it is put to exts, because metta-motto depends on it.
+Reagrding threading:
+- Generic threading for metta can be introduced with
+  parallel and sequential composition, for-comprehension, etc.
+  Agents could be built on top of this functionality. However,
+  this piece of code was driven by metta-motto demands.
+- Two main cases for agents are:
+  -- Immediate call with inputs to get outputs
+  -- Asynchronous events and responses
+  Supporting both cases in one implementation is more convenient,
+  because both of them can be needed simultaneously in certain
+  domains (e.g. metta-motto)
+- Implementation can be quite different.
+  -- Agents could be started explicitly
+  -- They could inherint from StreamMethod
+  -- Other methods could be called directly without StreamMethod wrapper
+  All these nuances are to be fleshed out
 '''
 
+import threading
+from queue import Queue
+class StreamMethod(threading.Thread):
+    def __init__(self, method, args):
+        super().__init__() #daemon=True
+        self._result = Queue()
+        self.method = method
+        self.args = args
+    def run(self):
+        for r in self.method(*self.args):
+            self._result.put(r)
+    def __iter__(self):
+        return self
+    def __next__(self):
+        if self._result.empty() and not self.is_alive():
+            raise StopIteration
+        return self._result.get()
+
 class AgentObject:
 
     '''
@@ -58,6 +92,9 @@ def _try_unwrap(self, val):
         return repr(val)
 
     def __init__(self, path=None, atoms={}, include_paths=None, code=None):
+        if path is None and code is None:
+            # purely Python agent
+            return
         # The first argument is either path or code when called from MeTTa
         if isinstance(path, ExpressionAtom):# and path != E():
             code = path
@@ -106,16 +143,28 @@ def __call__(self, atom):
             )
         return self._metta.evaluate_atom(atom)
 
+    def is_daemon(self):
+        return hasattr(self, 'daemon') and self.daemon is True
+
     def __metta_call__(self, *args):
+        call = True
         method = self.__call__
         if len(args) > 0 and isinstance(args[0], SymbolAtom):
             n = args[0].get_name()
             if n[0] == '.' and hasattr(self, n[1:]):
                 method = getattr(self, n[1:])
                 args = args[1:]
+                call = False
         if self._unwrap:
-            return OperationObject(f"{method}", method).execute(*args)
-        return method(*args)
+            method = OperationObject(f"{method}", method).execute
+        st = StreamMethod(method, args)
+        st.start()
+        # We don't return the stream here; otherwise it will be consumed immediately.
+        # If the agent itself would be StreamMethod, its results could be accessbile.
+        # Here, they are lost (TODO?).
+        if call and self.is_daemon():
+            return [E()]
+        return st
 
 
 @register_atoms(pass_metta=True)

python/hyperon/exts/agents/tests/test_agents.py

@@ -1,5 +1,7 @@
 from hyperon import MeTTa
 from hyperon.exts.agents import AgentObject
+from queue import Queue
+from time import sleep
 
 class MyAgent(AgentObject):
     '''
@@ -20,3 +22,70 @@ def __call__(self, a, b):
   ! (&agent 7 8)
   ! (&agent .subs 4)
 '''))
+
+# =================================
+
+class Agent1(AgentObject):
+    def __call__(self):
+        for x in range(10):
+            yield x
+            sleep(1)
+class Agent2(AgentObject):
+    def __call__(self, xs):
+        for x in xs:
+            yield x*2
+class Agent3(AgentObject):
+    def __call__(self, xs):
+        for x in xs:
+            print("Result: ", x)
+
+m = MeTTa()
+m.register_atom('new-agent-1', Agent1.agent_creator_atom())
+m.register_atom('new-agent-2', Agent2.agent_creator_atom())
+m.register_atom('new-agent-3', Agent3.agent_creator_atom())
+print(m.run('''
+  ! ((new-agent-3) ((new-agent-2) ((new-agent-1))))
+'''))
+
+# =================================
+
+class Agnt(AgentObject):
+    def __init__(self):
+        self.messages = Queue()
+        self.running = False
+        self.output = Queue()
+        self.daemon = True
+    def __call__(self):
+        self.running = True
+        cnt = 0
+        while self.running:
+            if self.messages.empty():
+                self.output.put(f"Waiting {cnt}")
+                sleep(2)
+                cnt += 1
+            else:
+                m = self.messages.get()
+                self.output.put(m[::-1])
+    def stop(self):
+        self.running = False
+    def input(self, msg):
+        self.messages.put(msg)
+    def response(self):
+        if self.output.empty():
+            return None
+        return self.output.get()
+
+m = MeTTa()
+m.register_atom('agnt', Agnt.agent_creator_atom())
+print(m.run('''
+  ! (bind! &a1 (agnt))
+  ! (&a1)
+  ! (println! "Agent is running")
+  ! ((py-atom time.sleep) 1)
+  ! ("First response:" (&a1 .response))
+  ! (&a1 .input "Hello")
+  ! (println! "Agent is receiving messages")
+  ! ((py-atom time.sleep) 2)
+  ! ("Second response:" (&a1 .response))
+  ! (&a1 .stop)
+'''))