diff --git a/pkg/types/cross.go b/pkg/types/cross.go
new file mode 100644
index 000000000..5504b035b
--- /dev/null
+++ b/pkg/types/cross.go
@@ -0,0 +1,56 @@
+package types
+
+// The result structure that maps to the crossing result of `CrossOver` and `CrossUnder`
+// Accessible through BoolSeries interface
+type CrossResult struct {
+	a      Series
+	b      Series
+	isOver bool
+}
+
+func (c *CrossResult) Last() bool {
+	if c.Length() == 0 {
+		return false
+	}
+	if c.isOver {
+		return c.a.Last(0)-c.b.Last(0) > 0 && c.a.Last(1)-c.b.Last(1) < 0
+	} else {
+		return c.a.Last(0)-c.b.Last(0) < 0 && c.a.Last(1)-c.b.Last(1) > 0
+	}
+}
+
+func (c *CrossResult) Index(i int) bool {
+	if i >= c.Length() {
+		return false
+	}
+	if c.isOver {
+		return c.a.Last(i)-c.b.Last(i) > 0 && c.a.Last(i+1)-c.b.Last(i+1) < 0
+	} else {
+		return c.a.Last(i)-c.b.Last(i) < 0 && c.a.Last(i+1)-c.b.Last(i+1) > 0
+	}
+}
+
+func (c *CrossResult) Length() int {
+	la := c.a.Length()
+	lb := c.b.Length()
+	if la > lb {
+		return lb
+	}
+	return la
+}
+
+// a series cross above b series.
+// If in current KLine, a is higher than b, and in previous KLine, a is lower than b, then return true.
+// Otherwise return false.
+// If accessing index <= length, will always return false
+func CrossOver(a Series, b Series) BoolSeries {
+	return &CrossResult{a, b, true}
+}
+
+// a series cross under b series.
+// If in current KLine, a is lower than b, and in previous KLine, a is higher than b, then return true.
+// Otherwise return false.
+// If accessing index <= length, will always return false
+func CrossUnder(a Series, b Series) BoolSeries {
+	return &CrossResult{a, b, false}
+}
diff --git a/pkg/types/indicator.go b/pkg/types/indicator.go
index 4dd396b05..593f6bec8 100644
--- a/pkg/types/indicator.go
+++ b/pkg/types/indicator.go
@@ -100,61 +100,6 @@ func NextCross(a Series, b Series, lookback int) (int, float64, bool) {
 	return int(math.Ceil(-indexf)), alpha1 + beta1*indexf, true
 }
 
-// The result structure that maps to the crossing result of `CrossOver` and `CrossUnder`
-// Accessible through BoolSeries interface
-type CrossResult struct {
-	a      Series
-	b      Series
-	isOver bool
-}
-
-func (c *CrossResult) Last() bool {
-	if c.Length() == 0 {
-		return false
-	}
-	if c.isOver {
-		return c.a.Last(0)-c.b.Last(0) > 0 && c.a.Last(1)-c.b.Last(1) < 0
-	} else {
-		return c.a.Last(0)-c.b.Last(0) < 0 && c.a.Last(1)-c.b.Last(1) > 0
-	}
-}
-
-func (c *CrossResult) Index(i int) bool {
-	if i >= c.Length() {
-		return false
-	}
-	if c.isOver {
-		return c.a.Last(i)-c.b.Last(i) > 0 && c.a.Last(i+1)-c.b.Last(i+1) < 0
-	} else {
-		return c.a.Last(i)-c.b.Last(i) < 0 && c.a.Last(i+1)-c.b.Last(i+1) > 0
-	}
-}
-
-func (c *CrossResult) Length() int {
-	la := c.a.Length()
-	lb := c.b.Length()
-	if la > lb {
-		return lb
-	}
-	return la
-}
-
-// a series cross above b series.
-// If in current KLine, a is higher than b, and in previous KLine, a is lower than b, then return true.
-// Otherwise return false.
-// If accessing index <= length, will always return false
-func CrossOver(a Series, b Series) BoolSeries {
-	return &CrossResult{a, b, true}
-}
-
-// a series cross under b series.
-// If in current KLine, a is lower than b, and in previous KLine, a is higher than b, then return true.
-// Otherwise return false.
-// If accessing index <= length, will always return false
-func CrossUnder(a Series, b Series) BoolSeries {
-	return &CrossResult{a, b, false}
-}
-
 func Highest(a Series, lookback int) float64 {
 	if lookback > a.Length() {
 		lookback = a.Length()