This package implements Finite State Transducers with the following characteristics:
FST Construction example:
// Input values (keys). These must be provided to Builder in Unicode sorted order!
String inputValues[] = {"cat", "dog", "dogs"};
long outputValues[] = {5, 7, 12};
PositiveIntOutputs outputs = PositiveIntOutputs.getSingleton();
Builder<Long> builder = new Builder<Long>(INPUT_TYPE.BYTE1, outputs);
BytesRef scratchBytes = new BytesRef();
IntsRef scratchInts = new IntsRef();
for (int i = 0; i < inputValues.length; i++) {
scratchBytes.copyChars(inputValues[i]);
builder.add(Util.toIntsRef(scratchBytes, scratchInts), outputValues[i]);
}
FST<Long> fst = builder.finish();
Retrieval by key:
Long value = Util.get(fst, new BytesRef("dog"));
System.out.println(value); // 7
Retrieval by value:
// Only works because outputs are also in sorted order
IntsRef key = Util.getByOutput(fst, 12);
System.out.println(Util.toBytesRef(key, scratchBytes).utf8ToString()); // dogs
Iterate over key-value pairs in sorted order:
// Like TermsEnum, this also supports seeking (advance)
BytesRefFSTEnum<Long> iterator = new BytesRefFSTEnum<Long>(fst);
while (iterator.next() != null) {
InputOutput<Long> mapEntry = iterator.current();
System.out.println(mapEntry.input.utf8ToString());
System.out.println(mapEntry.output);
}
N-shortest paths by weight:
Comparator<Long> comparator = new Comparator<Long>() {
public int compare(Long left, Long right) {
return left.compareTo(right);
}
};
Arc<Long> firstArc = fst.getFirstArc(new Arc<Long>());
MinResult<Long> paths[] = Util.shortestPaths(fst, firstArc, comparator, 2);
System.out.println(Util.toBytesRef(paths[0].input, scratchBytes).utf8ToString()); // cat
System.out.println(paths[0].output); // 5
System.out.println(Util.toBytesRef(paths[1].input, scratchBytes).utf8ToString()); // dog
System.out.println(paths[1].output); // 7