Modify iterators above to define a weak version which verifies only that events of type next(id) occur after events of type hasNext(id,true) and that the result of hasNext(id,res) can change only after next(id); multiple consecutive occurrences of events of type hasNext are allowed, as long as they are coherent, and iterators are not required to be fully consumed.

Solution

// iterators2: multiple iterators, weak version

// verifies only that next(id) occurs after hasNext(id,true) and that the result of hasNext(id,res) can change only after next(id)
// multiple consecutive occurrences of hasNext are allowed, as long as they are coherent
// iterators are not required to be fully consumed

Main = {let id; newIter(id)(Iterator<id> freeIter(id)|Main)}?;
Iterator<id> = ((hasNext(id,true)+ next(id))* hasNext(id,false)+)!;