stream_eval cleanup

Author: jorenham

unification/core.py

@@ -31,27 +31,27 @@ def stream_eval(z, res_filter=None):
     if not isinstance(z, Generator):
         return z
 
-    stack = deque()
+    stack = deque([z])
     z_args, z_out = None, None
-    stack.append(z)
 
     while stack:
         z = stack[-1]
         try:
             z_out = z.send(z_args)
 
-            if res_filter:
-                _ = res_filter(z, z_out)
+            if res_filter is not None:
+                res_filter(z, z_out)
 
+        except StopIteration:
+            stack.pop()
+
+        else:
             if isinstance(z_out, Generator):
                 stack.append(z_out)
                 z_args = None
             else:
                 z_args = z_out
 
-        except StopIteration:
-            _ = stack.pop()
-
     return z_out