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(defn auc [lines]
  (let [[a _ n fp' p tp'] (reduce iter [0 Double/NEGATIVE_INFINITY 0 0 0 0] lines)]
    (/ (+ a (trap-area n fp' n tp'))
       (* p n))))

defndaines

(defn iter
  "Area Under Curve [AUC] reduce function.
  The element is a vector of three elements: the ID of the model,
  whether the classifier example is positive (pos),
  and the probabilistic value (f).
  The accumulator tracks six values, aggregated area, the last f value (f'),
  negative examples (fp and fp'), and positive examples (tp and tp')."
  [[area f' fp fp' tp tp'] [_ pos f]]
  (if (= f' f)
    [area

defndaines

(defn trap-area
  "Trapezoid area."
  [x1 x2 y1 y2]
  (* (Math/abs (- x1 x2))
     (/ (+ y1 y2) 2)))

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    movie = Store.insert_movie(movie_map)

    movie_list = Eiga.Movie |> select([movie], movie.title) |> Eiga.Repo.all
    assert Enum.find(movie_list, &(&1 == movie_map["title"]))

    assert movie == Store.insert_movie(movie_map)
    assert Enum.filter(movie_list, &(&1 == movie_map["title"])) == [Enum.find(movie_list, &(&1 == movie_map["title"]))]

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    movie = Store.insert_movie(movie_map)

    movie_list = Eiga.Movie |> select([movie], movie.title) |> Eiga.Repo.all
    assert Enum.find(movie_list, &(&1 == movie_map["title"]))

    ^movie = Store.insert_movie(movie_map)
    assert Enum.filter(movie_list, &(&1 == movie_map["title"])) == [Enum.find(movie_list, &(&1 == movie_map["title"]))]

    Eiga.Repo.delete(movie)

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warning: variable movie is unused
  test/eiga/store_test.exs:22

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  test "inserting movies is idempotent" do
    movie_map = %{"title" => "The Goonies",
     "short_title" => "goonies",
     "year" => 1985,
     "country" => "U.S."}

    movie = Store.insert_movie(movie_map)

    movie_list = Eiga.Movie |> select([movie], movie.title) |> Eiga.Repo.all
    assert Enum.find(movie_list, &(&1 == movie_map["title"]))

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import java.util.LinkedList;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;

public final class Throttler {

    private final List<Throttle> throttles = new LinkedList<>();

    public void addThrottle(Throttle throttle) { throttles.add(throttle); }

defndaines

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

List<Double> doubles = Arrays.asList(3.0, 3.0, 3.0);
Optional<Double> pow = doubles.stream().reduce(Math::pow);

List<String> words = Arrays.asList("/a/", "b", "c");
Optional<String> result = words.stream().reduce(""::replaceFirst);

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import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Optional;

List<Long> numbers = Collections.emptyList();
Optional<Long> result = numbers.stream().reduce(Math::max);
// result.orElse(-1L) == -1L;

numbers = Arrays.asList(52L, 127L, 1337L);