// KindUint64 indicates that the type of the Value is a uint64.
	KindUint64

	// KindFloat64 indicates that the type of the Value is a float64.
	KindFloat64

	// KindFloat64Histogram indicates that the type of the Value is a *Float64Histogram.
	KindFloat64Histogram
)

// Value represents a metric value returned by the runtime.
type Value struct {
	kind    ValueKind
	scalar  uint64         // contains scalar values for scalar Kinds.

			"Bucket counts increase monotonically. " +
			"Note that this does not include tiny objects as defined by " +
			"/gc/heap/tiny/allocs:objects, only tiny blocks.",
		Kind:       KindFloat64Histogram,
		Cumulative: true,
	},
	{
		Name:        "/gc/heap/allocs:bytes",
		Description: "Cumulative sum of memory allocated to the heap by the application.",
		Kind:        KindUint64,
		Cumulative:  true,

		// Handle each sample.
		switch value.Kind() {
		case metrics.KindUint64:
			fmt.Printf("%s: %d\n", name, value.Uint64())
		case metrics.KindFloat64:
			fmt.Printf("%s: %f\n", name, value.Float64())
		case metrics.KindFloat64Histogram:
			// The histogram may be quite large, so let's just pull out
			// a crude estimate for the median for the sake of this example.
			fmt.Printf("%s: %f\n", name, medianBucket(value.Float64Histogram()))

				}
			case metrics.KindFloat64:
				new := vNew.Float64()
				old := vOld.Float64()
				if new < old {
					t.Errorf("%s decreased: %f < %f", name, new, old)
				}
			case metrics.KindFloat64Histogram:
				new := sum(vNew.Float64Histogram().Counts)
				old := sum(vOld.Float64Histogram().Counts)
				if new < old {
					t.Errorf("%s counts decreased: %d < %d", name, new, old)
				}
			}
		}
	}

pkg runtime/metrics, const KindBad ValueKind
pkg runtime/metrics, const KindFloat64 = 2
pkg runtime/metrics, const KindFloat64 ValueKind
pkg runtime/metrics, const KindFloat64Histogram = 3
pkg runtime/metrics, const KindFloat64Histogram ValueKind
pkg runtime/metrics, const KindUint64 = 1
pkg runtime/metrics, const KindUint64 ValueKind
pkg runtime/metrics, func All() []Description
pkg runtime/metrics, func Read([]Sample)

		{"Float64Histogram", Type, 16},
		{"Float64Histogram.Buckets", Field, 16},
		{"Float64Histogram.Counts", Field, 16},
		{"KindBad", Const, 16},
		{"KindFloat64", Const, 16},
		{"KindFloat64Histogram", Const, 16},
		{"KindUint64", Const, 16},
		{"Read", Func, 16},
		{"Sample", Type, 16},
		{"Sample.Name", Field, 16},
		{"Sample.Value", Field, 16},
		{"Value", Type, 16},