time sequence stuff

seq/seq.go

@@ -137,6 +137,22 @@ func (s Seq) MinMax() (min, max float64) {
 	return
 }
 
+// First returns the value at index 0.
+func (s Seq) First() float64 {
+	if s.Len() == 0 {
+		return 0
+	}
+	return s.GetValue(0)
+}
+
+// Last returns the value at index (len)-1.
+func (s Seq) Last() float64 {
+	if s.Len() == 0 {
+		return 0
+	}
+	return s.GetValue(s.Len() - 1)
+}
+
 // Sort returns the seq sorted in ascending order.
 // This fully enumerates the seq.
 func (s Seq) Sort() Seq {

seq/time_seq_test.go

@@ -40,6 +40,27 @@ func TestTimeSeqSort(t *testing.T) {
 	assert.Equal(max, last)
 }
 
+func TestTimeSeqSortDescending(t *testing.T) {
+	assert := assert.New(t)
+
+	seq := Times(
+		parseTime("2016-05-14 12:00:00"),
+		parseTime("2017-05-14 12:00:00"),
+		parseTime("2015-05-14 12:00:00"),
+		parseTime("2017-05-13 12:00:00"),
+	)
+
+	sorted := seq.SortDescending()
+	assert.Equal(4, sorted.Len())
+	min, max := sorted.MinAndMax()
+	assert.Equal(parseTime("2015-05-14 12:00:00"), min)
+	assert.Equal(parseTime("2017-05-14 12:00:00"), max)
+
+	first, last := sorted.First(), sorted.Last()
+	assert.Equal(max, first)
+	assert.Equal(min, last)
+}
+
 func TestTimeSeqDays(t *testing.T) {
 	assert := assert.New(t)