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  1. import java.util.*;
  2. import java.util.function.*;
  3. import java.util.stream.*;
  4.  
  5. class Mappers {
  6. 	public static final Function<List<IntUnaryOperator>, UnaryOperator<List<Integer>>> reduce =
  7. 		opList -> argList -> argList.stream()
  8. 			.flatMap(arg -> IntStream.range(0, opList.size())
  9. 				.mapToObj(iLastOp -> opList.subList(0, 1 + iLastOp).stream()
  10. 					.reduce(IntUnaryOperator::andThen).get()
  11. 					.applyAsInt(arg)))
  12. 			.collect(Collectors.toList());
  13.  
  14. 	public static final Function<List<IntUnaryOperator>, UnaryOperator<List<Integer>>> collect =
  15. 		opList -> argList -> argList.stream()
  16. 			.flatMap(arg -> opList.stream()
  17. 				.collect(Collector.of(
  18. 					ArrayList<Integer>::new,
  19. 					(a, b) -> a.add(b.applyAsInt(a.isEmpty() ? arg : a.get(a.size() - 1))),
  20. 					(a, b) -> { throw new UnsupportedOperationException(); }))
  21. 				.stream())
  22. 			.collect(Collectors.toList());
  23.  
  24. 	public static final Function<List<IntUnaryOperator>, UnaryOperator<List<Integer>>> sane =
  25. 		opList -> argList -> {
  26. 			var r = new ArrayList<Integer>();
  27. 			for (var arg : argList)
  28. 				for (var op : opList) {
  29. 					arg = op.applyAsInt(arg);
  30. 					r.add(arg);
  31. 				}
  32. 			return r;
  33. 		};
  34. }
  35.  
  36. class Main {
  37. 	public static void main(String[] args) {
  38. 		List.of(Mappers.reduce, Mappers.collect, Mappers.sane).forEach(mapper -> {
  39. 			var list = mapper.apply(List.of(x -> x, x -> x + 1, x -> x * x)).apply(List.of(1, 2));
  40. 			System.out.println(list);
  41. 		});
  42. 	}
  43. }
Success #stdin #stdout 0.1s 34408KB
comments ()
stdin 
Standard input is empty
stdout 
[1, 2, 4, 2, 3, 9]
[1, 2, 4, 2, 3, 9]
[1, 2, 4, 2, 3, 9]
https://ideone.com/WlgwvR
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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