From a1caabbd8ae439d2b897e6cb4e10ef8e96deb474 Mon Sep 17 00:00:00 2001
From: Simon Buerger <simonbuerger@users.noreply.github.com>
Date: Sat, 22 Jun 2019 21:13:59 +0200
Subject: [PATCH] Add Math.log() operator (#320)

I had a need for Math.log in an Animation calculation. This code all seemed to work and I think I found all the touch points, but I'm not well versed on the native side of things so please let me know if anything needs to change.
---
 README.md                                                | 9 +++++++++
 .../com/swmansion/reanimated/nodes/OperatorNode.java     | 8 ++++++++
 ios/Nodes/REAOperatorNode.m                              | 1 +
 mock.js                                                  | 1 +
 react-native-reanimated.d.ts                             | 1 +
 src/core/AnimatedOperator.js                             | 1 +
 src/operators.js                                         | 1 +
 7 files changed, 22 insertions(+)

diff --git a/README.md b/README.md
index 06db641c53b..dc792817b7f 100644
--- a/README.md
+++ b/README.md
@@ -416,6 +416,15 @@ sqrt(nodeOrNumber)
 
 The square root of the given node. If the number is negative, an error is thrown.
 
+---
+### `log`
+
+```js
+log(nodeOrNumber)
+```
+
+The log of the given node.
+
 ---
 ### `sin`
 
diff --git a/android/src/main/java/com/swmansion/reanimated/nodes/OperatorNode.java b/android/src/main/java/com/swmansion/reanimated/nodes/OperatorNode.java
index 45d8b947994..9d922c61af2 100644
--- a/android/src/main/java/com/swmansion/reanimated/nodes/OperatorNode.java
+++ b/android/src/main/java/com/swmansion/reanimated/nodes/OperatorNode.java
@@ -89,6 +89,12 @@ public double eval(Double x) {
       return Math.sqrt(x);
     }
   };
+  private static final Operator LOG = new SingleOperator() {
+    @Override
+    public double eval(Double x) {
+      return Math.log(x);
+    }
+  };
   private static final Operator SIN = new SingleOperator() {
     @Override
     public double eval(Double x) {
@@ -235,6 +241,8 @@ public OperatorNode(int nodeID, ReadableMap config, NodesManager nodesManager) {
       mOperator = MODULO;
     } else if ("sqrt".equals(op)) {
       mOperator = SQRT;
+    } else if ("log".equals(op)) {
+      mOperator = LOG;
     } else if ("sin".equals(op)) {
       mOperator = SIN;
     } else if ("cos".equals(op)) {
diff --git a/ios/Nodes/REAOperatorNode.m b/ios/Nodes/REAOperatorNode.m
index 35f3581f915..571a5d9e27b 100644
--- a/ios/Nodes/REAOperatorNode.m
+++ b/ios/Nodes/REAOperatorNode.m
@@ -45,6 +45,7 @@ - (instancetype)initWithID:(REANodeID)nodeID config:(NSDictionary<NSString *,id>
             @"pow": REA_REDUCE(pow(a, b)),
             @"modulo": REA_REDUCE(fmodf(fmodf(a, b) + b, b)),
             @"sqrt": REA_SINGLE(sqrt(a)),
+            @"log": REA_SINGLE(log(a)),
             @"sin": REA_SINGLE(sin(a)),
             @"cos": REA_SINGLE(cos(a)),
             @"tan": REA_SINGLE(tan(a)),
diff --git a/mock.js b/mock.js
index 43799901aec..a8c434228fe 100644
--- a/mock.js
+++ b/mock.js
@@ -52,6 +52,7 @@ module.exports = {
     pow: NOOP,
     modulo: NOOP,
     sqrt: NOOP,
+    log: NOOP,
     sin: NOOP,
     cos: NOOP,
     tan: NOOP,
diff --git a/react-native-reanimated.d.ts b/react-native-reanimated.d.ts
index 7a30d62a384..a7a782826fc 100644
--- a/react-native-reanimated.d.ts
+++ b/react-native-reanimated.d.ts
@@ -195,6 +195,7 @@ declare module 'react-native-reanimated' {
     export const pow: MultiOperator;
     export const modulo: MultiOperator;
     export const sqrt: UnaryOperator;
+    export const log: UnaryOperator;
     export const sin: UnaryOperator;
     export const cos: UnaryOperator;
     export const tan: UnaryOperator;
diff --git a/src/core/AnimatedOperator.js b/src/core/AnimatedOperator.js
index 90c47f8c0d4..c3c5f7db6b4 100644
--- a/src/core/AnimatedOperator.js
+++ b/src/core/AnimatedOperator.js
@@ -29,6 +29,7 @@ const OPERATIONS = {
   pow: reduce((a, b) => Math.pow(a, b)),
   modulo: reduce((a, b) => ((a % b) + b) % b),
   sqrt: single(a => Math.sqrt(a)),
+  log: single(a => Math.log(a)),
   sin: single(a => Math.sin(a)),
   cos: single(a => Math.cos(a)),
   tan: single(a => Math.tan(a)),
diff --git a/src/operators.js b/src/operators.js
index 44ac71fbff9..8b209a5c18d 100644
--- a/src/operators.js
+++ b/src/operators.js
@@ -9,6 +9,7 @@ export const divide = operator('divide');
 export const pow = operator('pow');
 export const modulo = operator('modulo');
 export const sqrt = operator('sqrt');
+export const log = operator('log');
 export const sin = operator('sin');
 export const cos = operator('cos');
 export const exp = operator('exp');