a4/code/src/learner/ExampleSUL.java

   1 package learner;
   2
   3 import de.learnlib.api.SUL;
   4 import de.learnlib.api.SULException;
   5
   6 /**
   7  * Example of a three-state system, hard-coded.
   8  *
   9  * @author Ramon Janssen
  10  */
  11 public class ExampleSUL implements SUL<String, String> {
  12         private enum State{s0,s1,s2};
  13         private State currentState;
  14         private static boolean VERBOSE = false;
  15
  16         @Override
  17         public void pre() {
  18                 // add any code here that should be run at the beginning of every 'session',
  19                 // i.e. put the system in its initial state
  20                 if (VERBOSE) {
  21                         System.out.println("Starting SUL");
  22                 }
  23                 currentState = State.s0;
  24         }
  25
  26         @Override
  27         public void post() {
  28                 // add any code here that should be run at the end of every 'session'
  29                 if (VERBOSE) {
  30                         System.out.println("Shutting down SUL");
  31                 }
  32         }
  33
  34         @Override
  35         public String step(String input) throws SULException {
  36                 State previousState = this.currentState;
  37                 String output = makeTransition(input);
  38                 State nextState = this.currentState;
  39                 if (VERBOSE) {
  40                         System.out.println(previousState + " --" + input + "/" + output + "-> " + nextState);
  41                 }
  42                 return output;
  43         }
  44
  45         /**
  46          * The behaviour of the SUL. It takes one input, and returns an output. It now
  47          * contains a hardcoded state-machine (so the result is easy to check). To learn
  48          * an external program/system, connect this method to the SUL (e.g. via sockets
  49          * or stdin/stdout) and make it perform an actual input, and retrieve an actual
  50          * output.
  51          * @param input
  52          * @return
  53          */
  54         public String makeTransition(String input) {
  55                 switch (currentState) {
  56                 case s0:
  57                         switch(input) {
  58                         case "a":
  59                                 currentState = State.s1;
  60                                 return "x";
  61                         case "b":
  62                                 currentState = State.s2;
  63                                 return "y";
  64                         case "c":
  65                                 return "z";
  66                         }
  67                 case s1:
  68                         switch(input) {
  69                         case "a":
  70                                 return "z";
  71                         case "b":
  72                                 currentState = State.s2;
  73                                 return "y";
  74                         case "c":
  75                                 return "z";
  76                         }
  77                 case s2:
  78                         switch(input) {
  79                         case "a":
  80                                 return "z";
  81                         case "b":
  82                                 currentState = State.s0;
  83                                 return "y";
  84                         case "c":
  85                                 return "z";
  86                         }
  87                 }
  88                 throw new SULException(new IllegalArgumentException("Argument '" + input + "' was not handled"));
  89         }
  90 }