import 'dart:async';
Future<int> sumStream(Stream<int> stream) async{
var sum=0;
await for(var value in stream){
sum += value;
}
return sum;
}
Stream<int> countStream(int to) async*{
for(int i=1;i<=to;i++){
yield i;
}
}
main(List<String> args) async{
var stream = countStream(10);
var sum = await sumStream(stream);
print(sum);
}