// Main function that user can call
static long stupidFib_collab(ICollab collab, int n) {
  ret collab_computeLong2(collab, continuation -> stupidFib_collab(collab, n, continuation));
}

// Work function used internally
svoid stupidFib_collab(ICollab collab, int n, LongConsumer continuation) {
  // switch to serial if no coworkers, OR if small enough work unit
  if (collab.singleCore() || n < 24) ret with continuation.accept(stupidFib(n));
  
  // recursion base
  if (n < 3) ret with continuation.accept(1);
  
  // recursion step
  var collector = longPairCollector((a, b) -> continuation.accept(a+b));
  collab.addWork(-> stupidFib_collab(collab, n-1, collector.a));
  collab.addWork(-> stupidFib_collab(collab, n-2, collector.b));
}

/*

// Both functions in one using the "parallel" modifier
static parallel long stupidFib_collab(int n) {
  // switch to serial if no coworkers, OR if small enough work unit
  if (collab.singleCore() || n < 24) ret stupidFib(n);
  
  // recursion base
  if (n < 3) ret 1;
  
  // recursion step
  var collector = longPairCollector((a, b) -> ret a+b);
  collab.addWork(-> stupidFib_collab(collab, n-1, collector.setA()));
  collab.addWork(-> stupidFib_collab(collab, n-2, collector.setB()));
}

*/

Began life as a copy of #1035566