package spike;

import com.jnape.palatable.lambda.adt.hlist.Tuple2;

import org.junit.Test;

import java.math.BigInteger;

import java.util.function.Function;

import static com.jnape.palatable.lambda.adt.hlist.HList.tuple;

import static com.jnape.palatable.lambda.functions.builtin.fn2.Into.into;

import static java.math.BigInteger.ONE;

import static org.junit.Assert.assertEquals;

import static spike.RecursiveResult.recurse;

import static spike.RecursiveResult.terminate;

import static spike.Trampoline.trampoline;

public class TrampolineTest {

private static final Function<Tuple2<BigInteger, BigInteger>, RecursiveResult<Tuple2<BigInteger, BigInteger>, BigInteger>> FACTORIAL =

into((x, acc) -> x.compareTo(ONE) > 0 ? recurse(tuple(x.subtract(ONE), x.multiply(acc))) : terminate(acc));

@Test

public void trampolinesCompatibleFunctionIntoResult() {

assertEquals(BigInteger.valueOf(3628800), trampoline(FACTORIAL, tuple(BigInteger.valueOf(10), ONE)));

}

@Test

public void stackSafety() {

trampoline(FACTORIAL, tuple(BigInteger.valueOf(10000), ONE));

}

}