*/
  public double populationCovariance() {
    checkState(count() != 0);
    return sumOfProductsOfDeltas / count();
  }

  /**
   * Returns the sample covariance of the values. The count must be greater than one.
   *
   * <p>This is not guaranteed to return zero when the dataset consists of the same pair of values
   * multiple times, due to numerical errors.
   *
   * <h3>Non-finite values</h3>
   *

package lifecycle

import (
	"encoding/xml"
	"time"
)

var (
	errTransitionInvalidDays     = Errorf("Days must be 0 or greater when used with Transition")
	errTransitionInvalidDate     = Errorf("Date must be provided in ISO 8601 format")
	errTransitionInvalid         = Errorf("Exactly one of Days (0 or greater) or Date (positive ISO 8601 format) should be present in Transition.")
	errTransitionDateNotMidnight = Errorf("'Date' must be at midnight GMT")

   * greater than or equal to that.
   */
  private static int partition(double[] array, int from, int to) {
    // Select a pivot, and move it to the start of the slice i.e. to index from.
    movePivotToStartOfSlice(array, from, to);
    double pivot = array[from];

    // Move all elements with indexes in (from, to] which are greater than the pivot to the end of

	Eq(neq).Build(builder)
}

// Gt greater than for where
type Gt Eq

func (gt Gt) Build(builder Builder) {
	builder.WriteQuoted(gt.Column)
	builder.WriteString(" > ")
	builder.AddVar(builder, gt.Value)
}

func (gt Gt) NegationBuild(builder Builder) {
	Lte(gt).Build(builder)
}

// Gte greater than or equal to for where
type Gte Eq

   */
  public double populationCovariance() {
    checkState(count() != 0);
    return sumOfProductsOfDeltas / count();
  }

  /**
   * Returns the sample covariance of the values. The count must be greater than one.
   *
   * <p>This is not guaranteed to return zero when the dataset consists of the same pair of values
   * multiple times, due to numerical errors.
   *
   * <h3>Non-finite values</h3>
   *

 * when {@code compare} is called on the above ordering:
 *
 * <ol>
 *   <li>First, if only one {@code Foo} is null, that null value is treated as <i>greater</i>
 *   <li>Next, non-null {@code Foo} values are passed to {@code getBarFunction} (we will be
 *       comparing {@code Bar} values from now on)

      }
    }
    return current;
  }

  /**
   * Returns the unique least value of type {@code C} that is greater than {@code value}, or {@code
   * null} if none exists. Inverse operation to {@link #previous}.
   *
   * @param value any value of type {@code C}
   * @return the least value greater than {@code value}, or {@code null} if {@code value} is {@code
   *     maxValue()}
   */
  @CheckForNull

 * when {@code compare} is called on the above ordering:
 *
 * <ol>
 *   <li>First, if only one {@code Foo} is null, that null value is treated as <i>greater</i>
 *   <li>Next, non-null {@code Foo} values are passed to {@code getBarFunction} (we will be
 *       comparing {@code Bar} values from now on)

  Set<E> inEdges();

  Set<E> outEdges();

  /**
   * Returns the set of edges connecting the origin node to {@code node}. For networks without
   * parallel edges, this set cannot be of size greater than one.
   */
  Set<E> edgesConnecting(N node);

  /**
   * Returns the node that is adjacent to the origin node along {@code edge}.
   *
   * <p>In the directed case, {@code edge} is assumed to be an outgoing edge.

 * using the latest values obtained from {@link IteratorTester#newTargetIterator()}.
 *
 * <p>The value you pass to the parameter {@code steps} should be greater than the length of your
 * iterator, so that this class can check that your iterator behaves correctly when it is exhausted.
 *
 * <p>For example, to test {@link java.util.Collections#unmodifiableList(java.util.List)