Added ThompsonConverter: Regex to NDFA

2017-05-17 14:52:49 +02:00
parent 83963f30dc
commit 6cff1d0766
4 changed files with 180 additions and 1 deletions
@@ -0,0 +1,150 @@
+package com.imegumii;
+
+/**
+ * Created by kenny on 17-5-2017.
+ */
+public class ThompsonConverter {
+
+    private static int count = 0;
+
+    public static NDFA<String> Convert(RegExp regex)
+    {
+        Character [] characters = {'a', 'b'};
+        NDFA generated = new NDFA<String>(characters);
+
+        ConvertStatement(regex, generated);
+
+        return generated;
+    }
+
+    private static void ConvertStatement(RegExp regex, NDFA automata)
+    {
+        switch(regex.operator)
+        {
+            case PLUS:
+
+                //Links
+                ConvertStatement(regex.links, automata);
+                String endLink1 = (String) automata.eindStates.first();
+                String beginLink1 = (String) automata.beginStates.first();
+
+                //Repeat and skip
+                automata.addTransition(new Transition(endLink1, Transition.EPSILON, beginLink1));
+
+                automata.clearEindStates();
+                automata.clearBeginStates();
+
+                automata.defineAsStartState(endLink1);
+                automata.defineAsEndState(beginLink1);
+
+                break;
+            case STER:
+
+                //Links
+                ConvertStatement(regex.links, automata);
+                String endLink2 = (String) automata.eindStates.first();
+                String beginLink2 = (String) automata.beginStates.first();
+
+                //New states
+                String start2 = getState();
+                String end2 = getState();
+
+                //Repeat and skip
+                automata.addTransition(new Transition(start2, Transition.EPSILON, end2));
+                automata.addTransition(new Transition(endLink2, Transition.EPSILON, beginLink2));
+                automata.addTransition(new Transition(start2, Transition.EPSILON, beginLink2));
+                automata.addTransition(new Transition(endLink2, Transition.EPSILON, end2));
+
+                automata.clearEindStates();
+                automata.clearBeginStates();
+
+                automata.defineAsStartState(start2);
+                automata.defineAsEndState(end2);
+
+                break;
+            case OF:
+
+                //Links
+                ConvertStatement(regex.links, automata);
+                String topEnd = (String) automata.eindStates.first();
+                String topBegin = (String) automata.beginStates.first();
+
+                //Rechts
+                ConvertStatement(regex.rechts, automata);
+                String bottomBegin = (String) automata.beginStates.first();
+                String bottomEnd = (String) automata.eindStates.first();
+
+                //New states
+                String start3 = getState();
+                String end3 = getState();
+
+                //Link both
+                automata.addTransition(new Transition(start3, Transition.EPSILON, topBegin));
+                automata.addTransition(new Transition(start3, Transition.EPSILON, bottomBegin));
+                automata.addTransition(new Transition(topEnd, Transition.EPSILON, end3));
+                automata.addTransition(new Transition(bottomEnd, Transition.EPSILON, end3));
+
+                automata.clearEindStates();
+                automata.clearBeginStates();
+
+                automata.defineAsStartState(start3);
+                automata.defineAsEndState(end3);
+
+
+                break;
+            case PUNT:
+
+                //Links
+                ConvertStatement(regex.links, automata);
+                String endLink = (String) automata.eindStates.first();
+                String newBeginLink = (String) automata.beginStates.first();
+
+                //Rechts
+                ConvertStatement(regex.rechts, automata);
+                String beginLink = (String) automata.beginStates.first();
+                String newEndLink = (String) automata.eindStates.first();
+
+                //Link both
+                automata.addTransition(new Transition(endLink, Transition.EPSILON, beginLink));
+
+                automata.clearEindStates();
+                automata.clearBeginStates();
+
+                automata.defineAsStartState(newBeginLink);
+                automata.defineAsEndState(newEndLink);
+
+                break;
+            case EEN:
+                char[] s = regex.characters.toCharArray();
+
+                automata.clearBeginStates();
+                automata.clearEindStates();
+
+                String prevState = getState();
+                String newState = "";
+                automata.defineAsStartState(prevState);
+
+                for(char c : s)
+                {
+                    newState = getState();
+                    Transition<String> t = new Transition<String>(prevState, c, newState);
+                    prevState = newState;
+                    automata.addTransition(t);
+                }
+
+                automata.defineAsEndState(newState);
+
+                break;
+            default:
+                System.out.println("Error #8.1");
+                break;
+        }
+    }
+
+    private static String getState()
+    {
+        count++;
+        return "q" + count;
+    }
+
+}