tweak repr, doc

src/kyupy/circuit.py

@@ -82,6 +82,8 @@ class Node:
     def __repr__(self):
         ins = ' '.join([f'<{line.index}' if line is not None else '<None' for line in self.ins])
         outs = ' '.join([f'>{line.index}' if line is not None else '>None' for line in self.outs])
+        ins = ' ' + ins if len(ins) else ''
+        outs = ' ' + outs if len(outs) else ''
         return f'{self.index}:{self.kind}"{self.name}"{ins}{outs}'
 
     def remove(self):

src/kyupy/sim.py

@@ -237,7 +237,7 @@ class SimOps:
         self.level_starts = np.asarray(level_starts, dtype='int32')
         self.level_stops = np.asarray(level_starts[1:] + [len(self.ops)], dtype='int32')
 
-        # state allocation table. maps line and interface indices to self.state memory locations
+        # combinational signal allocation table. maps line and interface indices to self.c memory locations
         self.c_locs = np.full((self.c_locs_len,), -1, dtype=np.int32)
         self.c_caps = np.zeros((self.c_locs_len,), dtype=np.int32)