Clean up interpolate

* Don't glom properties onto a function; flow doesn't handle this well.
* Remove unused vec2 function.

src/geo/transform.js

@@ -4,7 +4,7 @@ const LngLat = require('./lng_lat'),
     Point = require('@mapbox/point-geometry'),
     Coordinate = require('./coordinate'),
     util = require('../util/util'),
-    interp = require('../style-spec/util/interpolate'),
+    interp = require('../style-spec/util/interpolate').number,
     TileCoord = require('../source/tile_coord'),
     EXTENT = require('../data/extent'),
     glmatrix = require('@mapbox/gl-matrix');

src/style-spec/util/interpolate.js

@@ -2,32 +2,27 @@
 
 const Color = require('./color');
 
-module.exports = interpolate;
+module.exports = {
+    number,
+    color,
+    array
+};
 
-function interpolate(a: number, b: number, t: number) {
+function number(a: number, b: number, t: number) {
     return (a * (1 - t)) + (b * t);
 }
 
-interpolate.number = interpolate;
-
-interpolate.vec2 = function(from: [number, number], to: [number, number], t: number) {
-    return [
-        interpolate(from[0], to[0], t),
-        interpolate(from[1], to[1], t)
-    ];
-};
-
-interpolate.color = function(from: Color, to: Color, t: number) {
+function color(from: Color, to: Color, t: number) {
     return new Color(
-        interpolate(from.r, to.r, t),
-        interpolate(from.g, to.g, t),
-        interpolate(from.b, to.b, t),
-        interpolate(from.a, to.a, t)
+        number(from.r, to.r, t),
+        number(from.g, to.g, t),
+        number(from.b, to.b, t),
+        number(from.a, to.a, t)
     );
-};
+}
 
-interpolate.array = function(from: Array<number>, to: Array<number>, t: number) {
+function array(from: Array<number>, to: Array<number>, t: number) {
     return from.map((d, i) => {
-        return interpolate(d, to[i], t);
+        return number(d, to[i], t);
     });
-};
+}

src/style/style_transition.js

@@ -87,7 +87,7 @@ class StyleTransition {
 
         const timeFraction = Math.min((Date.now() - this.zoomHistory.lastIntegerZoomTime) / this.duration, 1);
         const zoomFraction = Math.abs(z - lastIntegerZoom);
-        const t = interpolate(timeFraction, 1, zoomFraction);
+        const t = interpolate.number(timeFraction, 1, zoomFraction);
 
         if (from === undefined || to === undefined)
             return undefined;

src/symbol/get_anchors.js

@@ -1,6 +1,6 @@
 // @flow
 
-const interpolate = require('../style-spec/util/interpolate');
+const interpolate = require('../style-spec/util/interpolate').number;
 const Anchor = require('../symbol/anchor');
 const checkMaxAngle = require('./check_max_angle');
 

src/ui/camera.js

@@ -1,7 +1,7 @@
 // @flow
 
 const util = require('../util/util');
-const interpolate = require('../style-spec/util/interpolate');
+const interpolate = require('../style-spec/util/interpolate').number;
 const browser = require('../util/browser');
 const LngLat = require('../geo/lng_lat');
 const LngLatBounds = require('../geo/lng_lat_bounds');

test/unit/style-spec/interpolate.test.js

@@ -4,21 +4,11 @@ const test = require('mapbox-gl-js-test').test;
 const interpolate = require('../../../src/style-spec/util/interpolate');
 const Color = require('../../../src/style-spec/util/color');
 
-test('interpolate.number', (t) => {
-    t.equal(interpolate(0, 1, 0.5), 0.5);
-    t.end();
-});
-
 test('interpolate.number', (t) => {
     t.equal(interpolate.number(0, 1, 0.5), 0.5);
     t.end();
 });
 
-test('interpolate.vec2', (t) => {
-    t.deepEqual(interpolate.vec2([0, 0], [1, 2], 0.5), [0.5, 1]);
-    t.end();
-});
-
 test('interpolate.color', (t) => {
     t.deepEqual(interpolate.color(new Color(0, 0, 0, 0), new Color(1, 2, 3, 4), 0.5), new Color(0.5, 1, 3 / 2, 2));
     t.end();