Trampoline : Stackless Recursion for Java 8
A Trampoline captures the state of a computation - either done / or more to do.
Trampolines can be used to turn tail recursive calls into a more iterative form, lessening the likelihood of StackOverflow errors
@Test
public void trampolineTest(){
assertThat(loop(500000,10).result(),equalTo(446198426));
}
Trampoline<Integer> loop(int times,int sum){
if(times==0)
return Trampoline.done(sum);
else
return Trampoline.more(()->loop(times-1,sum+times));
}The code above could be further simplified using static imports
@Test
public void trampolineTest(){
assertThat(loop(500000,10).result(),equalTo(446198426));
}
Trampoline<Integer> loop(int times,int sum){
if(times==0)
return done(sum);
else
return more(()->loop(times-1,sum+times));
}Trampolines can be used to interleave the execution of different functions on the same thread, in a generic if ugly way
List results;
@Test
public void coroutine(){
results = new ArrayList();
Iterator<String> it = Arrays.asList("hello","world","end").iterator();
Trampoline[] coroutine = new Trampoline[1];
coroutine[0] = Trampoline.more( ()-> it.hasNext() ? print(it.next(),coroutine[0]) : Trampoline.done(0));
withCoroutine(coroutine[0]);
assertThat(results,equalTo(Arrays.asList(0,"hello",1,"world",2,"end",3,4)));
}
private Trampoline<Integer> print(Object next, Trampoline trampoline) {
System.out.println(next);
results.add(next);
return trampoline;
}
public void withCoroutine(Trampoline coroutine){
for(int i=0;i<5;i++){
print(i,coroutine);
if(!coroutine.complete())
coroutine= coroutine.bounce();
}
}