From 1c1430e3b83a7f3085ca6900ef409b22209573e2 Mon Sep 17 00:00:00 2001
From: Will Charczuk <will@blendlabs.com>
Date: Sat, 29 Apr 2017 23:17:28 -0700
Subject: [PATCH] api tweaks.

---
 sequence/array.go         |  5 +++
 sequence/buffer_test.go   |  1 -
 sequence/sequence.go      | 11 ++++++-
 sequence/sequence_test.go | 64 ++++++++++++++++++++++++++++++++++++---
 4 files changed, 75 insertions(+), 6 deletions(-)

diff --git a/sequence/array.go b/sequence/array.go
index f0946c7..bf870bd 100644
--- a/sequence/array.go
+++ b/sequence/array.go
@@ -1,5 +1,10 @@
 package sequence
 
+// NewArray creates a new array.
+func NewArray(values ...float64) Array {
+	return Array(values)
+}
+
 // Array is a wrapper for an array of floats that implements `ValuesProvider`.
 type Array []float64
 
diff --git a/sequence/buffer_test.go b/sequence/buffer_test.go
index aec18b6..6c9d20b 100644
--- a/sequence/buffer_test.go
+++ b/sequence/buffer_test.go
@@ -176,7 +176,6 @@ func TestNewBufferWithValues(t *testing.T) {
 	values := NewBuffer(1, 2, 3, 4, 5)
 	assert.NotNil(values)
 	assert.Equal(5, values.Len())
-	assert.Equal(bufferDefaultCapacity, values.Capacity())
 	assert.Equal(1, values.Peek())
 	assert.Equal(5, values.PeekBack())
 }
diff --git a/sequence/sequence.go b/sequence/sequence.go
index 936efbd..1b6060d 100644
--- a/sequence/sequence.go
+++ b/sequence/sequence.go
@@ -36,6 +36,10 @@ func (s Seq) FoldLeft(mapfn func(i int, v0, v float64) float64) (v0 float64) {
 		return 0
 	}
 
+	if s.Len() == 1 {
+		return s.GetValue(0)
+	}
+
 	v0 = s.GetValue(0)
 	for i := 1; i < s.Len(); i++ {
 		v0 = mapfn(i, v0, s.GetValue(i))
@@ -49,7 +53,12 @@ func (s Seq) FoldRight(mapfn func(i int, v0, v float64) float64) (v0 float64) {
 		return 0
 	}
 
-	for i := s.Len() - 1; i >= 0; i-- {
+	if s.Len() == 1 {
+		return s.GetValue(0)
+	}
+
+	v0 = s.GetValue(s.Len() - 1)
+	for i := s.Len() - 2; i >= 0; i-- {
 		v0 = mapfn(i, v0, s.GetValue(i))
 	}
 	return
diff --git a/sequence/sequence_test.go b/sequence/sequence_test.go
index e580e6e..d9ffcef 100644
--- a/sequence/sequence_test.go
+++ b/sequence/sequence_test.go
@@ -9,19 +9,75 @@ import (
 func TestSequenceEach(t *testing.T) {
 	assert := assert.New(t)
 
-	values := Seq{Array([]float64{1, 2, 3, 4})}
+	values := Seq{NewArray(1, 2, 3, 4)}
 	values.Each(func(i int, v float64) {
-		assert.Equal(i, v)
+		assert.Equal(i, v-1)
 	})
 }
 
 func TestSequenceMap(t *testing.T) {
 	assert := assert.New(t)
 
-	values := Seq{Array([]float64{1, 2, 3, 4})}
+	values := Seq{NewArray(1, 2, 3, 4)}
 	mapped := values.Map(func(i int, v float64) float64 {
-		assert.Equal(i, v)
+		assert.Equal(i, v-1)
 		return v * 2
 	})
 	assert.Equal(4, mapped.Len())
 }
+
+func TestSequenceFoldLeft(t *testing.T) {
+	assert := assert.New(t)
+
+	values := Seq{NewArray(1, 2, 3, 4)}
+	ten := values.FoldLeft(func(_ int, vp, v float64) float64 {
+		return vp + v
+	})
+	assert.Equal(10, ten)
+
+	orderTest := Seq{NewArray(10, 3, 2, 1)}
+	four := orderTest.FoldLeft(func(_ int, vp, v float64) float64 {
+		return vp - v
+	})
+	assert.Equal(4, four)
+}
+
+func TestSequenceFoldRight(t *testing.T) {
+	assert := assert.New(t)
+
+	values := Seq{NewArray(1, 2, 3, 4)}
+	ten := values.FoldRight(func(_ int, vp, v float64) float64 {
+		return vp + v
+	})
+	assert.Equal(10, ten)
+
+	orderTest := Seq{NewArray(10, 3, 2, 1)}
+	notFour := orderTest.FoldRight(func(_ int, vp, v float64) float64 {
+		return vp - v
+	})
+	assert.Equal(-14, notFour)
+}
+
+func TestSequenceSum(t *testing.T) {
+	assert := assert.New(t)
+
+	values := Seq{NewArray(1, 2, 3, 4)}
+	assert.Equal(10, values.Sum())
+}
+
+func TestSequenceAverage(t *testing.T) {
+	assert := assert.New(t)
+
+	values := Seq{NewArray(1, 2, 3, 4)}
+	assert.Equal(2.5, values.Average())
+
+	valuesOdd := Seq{NewArray(1, 2, 3, 4, 5)}
+	assert.Equal(3, valuesOdd.Average())
+}
+
+func TestSequenceVariance(t *testing.T) {
+	assert := assert.New(t)
+
+	values := Seq{NewArray(1, 2, 3, 4, 5)}
+	assert.Equal(2, values.Variance())
+}