How to use an AFD Create a new AFD in this case is of type Character so the transitions will be of characters (used in compilers for example)
AFD<Character>afd;
afd = new AFD<>() {
@Override
public void onReadSequence(List<Character> completeSequence, State<Character> finalNode, int statusCode) {
System.out.println(completeSequence+" Status code: "+statusCode);
}
};Must override onReadSequence(). This method will be called when the AFD detect a new sequence (The AFD finish in an end state). It will give the finalNode the list of characters that were detected and a status code to know how it finished.
Now we need to create the states and transitions of the AFD. Note: the algorithm doesn't check infinite loops (you should create a non cyclic structure to be an AFD)
To create an State and add a transition to another node (in this case from base to dollar)
State<Character> base = new State<>("root");
State<Character> dollar = new State<>("dollar");
base.addTransition('$',dollar);Transition functions are supported. Imagine you want to make a transition if characters are digits: Create the function (in this case is create in the main class RuleAnalyzer)
public static boolean isDigit(Character character){
return(Character.isDigit(character));
}And add the transition to the state determined by the function, the out state and read and write (boolean). Write must be used in final states
base.addTransitionFunction(RuleAnalyzer::isDigit, dollar,true,true);If you want to make an state final just call the method setFinal.
dollar.setFinal();Semantic actions are supported:
dollar.addSemanticAction(new SemanticAction<Character>() {
@Override
public void onAction(List<Character> sequence, State<Character> state) {
Stream<Character> charStream = sequence.stream();
String symbol = charStream.map(String::valueOf).collect(Collectors.joining());
variables.putSymbol(symbol.trim());
setToken(StateCodes.VARIABLE.ordinal());
}
});When the node dollar is reached onAction will be called with the current sequence detected and the state.
Its important to set the initial state of the AFD.
afd.setRoot(base);Now the AFD is done. To execute it just call execute method of the AFD:
private static int interpret(String ruleElement){
return afd.execute(toCharacterArray(ruleElement));
}Where toCharacterArray will convert the String in a Character[]sequence which is neccessary for the AFD
public static Character[] toCharacterArray(String text){
return text.chars().mapToObj(c -> (char) c).toArray(Character[]::new);
}If you turn on the DEBUG you will be able to test and debug the algorithm
