builtins: add Geography builtins

pkg/geo/geogfn/distance.go

@@ -20,18 +20,9 @@ import (
 	"github.com/golang/geo/s2"
 )
 
-type useSphereOrSpheroid bool
-
-const (
-	// UseSpheroid indicates to use the spheroid for calculations.
-	UseSpheroid useSphereOrSpheroid = true
-	// UseSphere indicates to use the sphere for calculations.
-	UseSphere useSphereOrSpheroid = false
-)
-
 // Distance returns the distance between geographies a and b on a sphere or spheroid.
 func Distance(
-	a *geo.Geography, b *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid,
+	a *geo.Geography, b *geo.Geography, useSphereOrSpheroid UseSphereOrSpheroid,
 ) (float64, error) {
 	if a.SRID() != b.SRID() {
 		return 0, geo.NewMismatchingSRIDsError(a, b)

pkg/geo/geogfn/distance_test.go

@@ -235,7 +235,7 @@ func TestDistance(t *testing.T) {
 			for _, subTC := range []struct {
 				desc                string
 				expected            float64
-				useSphereOrSpheroid useSphereOrSpheroid
+				useSphereOrSpheroid UseSphereOrSpheroid
 			}{
 				{"sphere", tc.expectedSphereDistance, UseSphere},
 				{"spheroid", tc.expectedSpheroidDistance, UseSpheroid},

pkg/geo/geogfn/dwithin.go

@@ -19,7 +19,7 @@ import (
 
 // DWithin returns whether a is within distance d of b, i.e. Distance(a, b) <= d.
 func DWithin(
-	a *geo.Geography, b *geo.Geography, distance float64, useSphereOrSpheroid useSphereOrSpheroid,
+	a *geo.Geography, b *geo.Geography, distance float64, useSphereOrSpheroid UseSphereOrSpheroid,
 ) (bool, error) {
 	if a.SRID() != b.SRID() {
 		return false, geo.NewMismatchingSRIDsError(a, b)

pkg/geo/geogfn/dwithin_test.go

@@ -34,7 +34,7 @@ func TestDWithin(t *testing.T) {
 			for _, subTC := range []struct {
 				desc                string
 				expected            float64
-				useSphereOrSpheroid useSphereOrSpheroid
+				useSphereOrSpheroid UseSphereOrSpheroid
 			}{
 				{"sphere", tc.expectedSphereDistance, UseSphere},
 				{"spheroid", tc.expectedSpheroidDistance, UseSpheroid},

pkg/geo/geogfn/geogfn.go

@@ -0,0 +1,22 @@
+// Copyright 2020 The Cockroach Authors.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.txt.
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0, included in the file
+// licenses/APL.txt.
+
+package geogfn
+
+// UseSphereOrSpheroid indicates whether to use a Sphere or Spheroid
+// for certain calculations.
+type UseSphereOrSpheroid bool
+
+const (
+	// UseSpheroid indicates to use the spheroid for calculations.
+	UseSpheroid UseSphereOrSpheroid = true
+	// UseSphere indicates to use the sphere for calculations.
+	UseSphere UseSphereOrSpheroid = false
+)

pkg/geo/geogfn/unary_operators.go

@@ -19,7 +19,7 @@ import (
 )
 
 // Area returns the area of a given Geography.
-func Area(g *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid) (float64, error) {
+func Area(g *geo.Geography, useSphereOrSpheroid UseSphereOrSpheroid) (float64, error) {
 	regions, err := g.AsS2()
 	if err != nil {
 		return 0, err
@@ -51,7 +51,7 @@ func Area(g *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid) (float64, e
 }
 
 // Perimeter returns the perimeter of a given Geography.
-func Perimeter(g *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid) (float64, error) {
+func Perimeter(g *geo.Geography, useSphereOrSpheroid UseSphereOrSpheroid) (float64, error) {
 	gt, err := g.AsGeomT()
 	if err != nil {
 		return 0, err
@@ -67,7 +67,7 @@ func Perimeter(g *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid) (float
 }
 
 // Length returns length of a given Geography.
-func Length(g *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid) (float64, error) {
+func Length(g *geo.Geography, useSphereOrSpheroid UseSphereOrSpheroid) (float64, error) {
 	gt, err := g.AsGeomT()
 	if err != nil {
 		return 0, err
@@ -84,7 +84,7 @@ func Length(g *geo.Geography, useSphereOrSpheroid useSphereOrSpheroid) (float64,
 
 // length returns the sum of the lengtsh and perimeters in the shapes of the Geography.
 // In OGC parlance, length returns both LineString lengths _and_ Polygon perimeters.
-func length(regions []s2.Region, useSphereOrSpheroid useSphereOrSpheroid) (float64, error) {
+func length(regions []s2.Region, useSphereOrSpheroid UseSphereOrSpheroid) (float64, error) {
 	spheroid := geographiclib.WGS84Spheroid
 
 	var totalLength float64

pkg/geo/geogfn/unary_operators_test.go

@@ -109,7 +109,7 @@ func TestArea(t *testing.T) {
 
 			for _, subTC := range []struct {
 				desc                string
-				useSphereOrSpheroid useSphereOrSpheroid
+				useSphereOrSpheroid UseSphereOrSpheroid
 				expected            float64
 			}{
 				{"sphere", UseSphere, tc.sphere.expectedArea},
@@ -140,7 +140,7 @@ func TestPerimeter(t *testing.T) {
 
 			for _, subTC := range []struct {
 				desc                string
-				useSphereOrSpheroid useSphereOrSpheroid
+				useSphereOrSpheroid UseSphereOrSpheroid
 				expected            float64
 			}{
 				{"sphere", UseSphere, tc.sphere.expectedPerimeter},
@@ -171,7 +171,7 @@ func TestLength(t *testing.T) {
 
 			for _, subTC := range []struct {
 				desc                string
-				useSphereOrSpheroid useSphereOrSpheroid
+				useSphereOrSpheroid UseSphereOrSpheroid
 				expected            float64
 			}{
 				{"sphere", UseSphere, tc.sphere.expectedLength},