some typing fixes, no more empty automata

demo.py

 from parser import Parser
-from objects import Terminal, Nonterminal, State, DFA, REG, NFA
+from objects import Character, Terminal, Nonterminal, State, DFA, REG, NFA
 from objects import Composition as comp
 from typing import Set, Dict, Tuple
 
 
-def make_dfa(states: Set[str], terminals: Set[str],
+def make_dfa(states: Set[str], characters: Set[str],
              transition: Dict[Tuple[str, str], str], init: str, final: Set[str]):
-    dfa = DFA(set(), set(), {}, None, set())
-    dfa.init = State(init)
+
+    new_init = State(init)
+    new_states: Set[State] = set()
+    dfa = DFA(new_states.add(new_init), set(), {}, new_init, set())
 
     for name in states:
         state = State(name)
         dfa.states.add(state)
-    for name in terminals:
-        terminal = Terminal(name)
-        dfa.terminals.add(terminal)
+    for name in characters:
+        character = Character(name)
+        dfa.characters.add(character)
     for name in final:
         state = State(name)
         dfa.final.add(state)
     for x, y in transition:
         state = State(x)
-        terminal = Terminal(y)
+        character = Character(y)
         move = State(transition[x, y])
-        dfa.transition[state, terminal] = move
+        dfa.transition[state, character] = move
 
+    dfa.check()
     return dfa
 
 
@@ -94,7 +97,7 @@ def main():
     print("Add new terminal for DFA, check its totality, then make total.")
     print()
     b = Terminal("b")
-    dfa_1.terminals.add(b)
+    dfa_1.characters.add(b)
     print("dfa_1.terminals.add(b), dfa_1.is_total():", dfa_1.is_total())
     print()
     total_dfa = dfa_1.total()
@@ -189,5 +192,13 @@ def main():
     #det = nfa1.determinize()
     #print(parser.dfa_to_str(det, True))
 
+    print("__________________________________")
+    print("DFA.is_equivalent()")
+    print("Equivalence of DFAs through intersections with complements.")
+    print()
+
+    print(dfa_3.is_equivalent(canonical), ", should be True")
+    print()
+
 
 main()
\ No newline at end of file

parser.py

@@ -62,15 +62,15 @@ class Parser:
 
         # Vlada: states = ",".join(dfa.states) but I use it wrong or what
 
-        terminals = "{"
-        for terminal in dfa.terminals:
-            terminals += terminal.name + ","
-        terminals = terminals[:-1] + "}"
+        characters = "{"
+        for character in dfa.characters:
+            characters += character.name + ","
+        characters = characters[:-1] + "}"
 
         transition = ""
         for key, state_2 in dfa.transition.items():
-            state_1, terminal = key
-            transition += "(" + state_1.name + "," + terminal.name + ")=" + state_2.name + "\n"
+            state_1, character = key
+            transition += "(" + state_1.name + "," + character.name + ")=" + state_2.name + "\n"
         transition = "{" + transition[:-1] + "}"
 
         init = dfa.init.name
@@ -81,7 +81,7 @@ class Parser:
         final = final[:-1] + "}"
 
         if full:
-            return "DFA = (" + states + "," + terminals + ",d," + \
+            return "DFA = (" + states + "," + characters + ",d," + \
                    init + "," + final + ")\n" + "d = " + transition
 
         else:
@@ -99,10 +99,10 @@ class Parser:
 
         # Vlada: states = ",".join(dfa.states) but I use it wrong or what
 
-        terminals = "{"
-        for terminal in dfa.terminals:
-            terminals += terminal.name + ","
-        terminals = terminals[:-1] + "}"
+        characters = "{"
+        for character in dfa.characters:
+            characters += character.name + ","
+        characters = characters[:-1] + "}"
 
         transition = ""
         for key, set_states in dfa.transition.items():
@@ -121,7 +121,7 @@ class Parser:
         final = final[:-1] + "}"
 
         if full:
-            return "NFA = (" + states + "," + terminals + ",d," + \
+            return "NFA = (" + states + "," + characters + ",d," + \
                    init + "," + final + ")\n" + "d = " + transition
 
         else: