From 767789235fbbfed29ee256621f2a171f04d29913 Mon Sep 17 00:00:00 2001
From: Julien Vincent <julienlucvincent@gmail.com>
Date: Sun, 14 May 2017 16:50:55 +0200
Subject: [PATCH 1/2] Introduced ability to declare a custom interpolator

---
 src/Interpolation.js | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/Interpolation.js b/src/Interpolation.js
index 315d596..8bf4784 100644
--- a/src/Interpolation.js
+++ b/src/Interpolation.js
@@ -24,7 +24,7 @@ export type InterpolationConfigType = {
   extrapolate?: ExtrapolateType;
   extrapolateLeft?: ExtrapolateType;
   extrapolateRight?: ExtrapolateType;
-};
+} | (input: number) => number | string;
 
 var linear = (t) => t;
 
@@ -35,6 +35,17 @@ var linear = (t) => t;
 class Interpolation {
   static create(config: InterpolationConfigType): (input: number) => number | string {
 
+    if (typeof config === 'function') {
+      const result = config(input);
+
+      invariant(
+        typeof result === 'string' || typeof result === 'number',
+        'Custom interpolator must return a string or a number'
+      );
+
+      return result;
+    }
+
     if (config.outputRange && typeof config.outputRange[0] === 'string') {
       return createInterpolationFromStringOutputRange(config);
     }

From 12ab5199f6b5c15a2ee68f018e299406e1f22ef3 Mon Sep 17 00:00:00 2001
From: Julien Vincent <julienlucvincent@gmail.com>
Date: Sun, 14 May 2017 17:29:50 +0200
Subject: [PATCH 2/2] fix: Interpolation.create expects a function

---
 src/Interpolation.js | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/Interpolation.js b/src/Interpolation.js
index 8bf4784..0a7fb33 100644
--- a/src/Interpolation.js
+++ b/src/Interpolation.js
@@ -36,14 +36,16 @@ class Interpolation {
   static create(config: InterpolationConfigType): (input: number) => number | string {
 
     if (typeof config === 'function') {
-      const result = config(input);
+      return (input: number) => {
+        const result = config(input);
 
-      invariant(
-        typeof result === 'string' || typeof result === 'number',
-        'Custom interpolator must return a string or a number'
-      );
+        invariant(
+          typeof result === 'string' || typeof result === 'number',
+          'Custom interpolator must return a string or a number'
+        );
 
-      return result;
+        return result;
+      };
     }
 
     if (config.outputRange && typeof config.outputRange[0] === 'string') {