From b305d2611f7256fdd0608f945c7b0984151e064c Mon Sep 17 00:00:00 2001
From: Evert Pot <me@evertpot.com>
Date: Sat, 1 Aug 2020 16:42:08 -0400
Subject: [PATCH 1/4] POW operation.

This is a first slow version. Lets see if we can speed this up.

Fixes #35
---
 .eslintrc.json |  5 +++--
 src/money.ts   | 31 +++++++++++++++++++++++++++++++
 test/money.ts  | 25 +++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/.eslintrc.json b/.eslintrc.json
index a3ccd87..a3d3ea1 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -45,6 +45,7 @@
           "ts-expect-error": "allow-with-description"
         }
       ],
-      "@typescript-eslint/no-explicit-any" : 0
+      "@typescript-eslint/no-explicit-any" : 0,
+      "@typescript-eslint/no-this-alias": 0
   }
-}
\ No newline at end of file
+}
diff --git a/src/money.ts b/src/money.ts
index 44d36cd..e6b4844 100644
--- a/src/money.ts
+++ b/src/money.ts
@@ -110,6 +110,37 @@ export class Money {
 
   }
 
+  /**
+   * Pow returns the current value to it's exponent.
+   *
+   * pow currently only supports whole numbers.
+   */
+  pow(exponent: number): Money {
+
+    if (!Number.isInteger(exponent)) {
+      throw new Error('You can currently only use pow() with whole numbers');
+    }
+
+    if (exponent===1) {
+      return this;
+    } else if (exponent === 0) {
+      return new Money(1, this.currency);
+    } else if (exponent > 1) {
+      let base:Money = this;
+      for(let i = 1; i < exponent; i++) {
+        base = base.multiply(this);
+      }
+      return base;
+    } else {
+      let base:Money = this;
+      for(let i = 1; i > exponent; i--) {
+        base = base.divide(this);
+      }
+      return base;
+    }
+
+  }
+
   /**
    * Returns the absolute value.
    */
diff --git a/test/money.ts b/test/money.ts
index 797a696..1577e65 100644
--- a/test/money.ts
+++ b/test/money.ts
@@ -287,6 +287,31 @@ describe('Money class', () => {
 
   });
 
+  describe('pow', () => {
+
+    const cases: [string|number, number, string][] = [
+      ['1',  5,'1.00'],
+      ['2',  8, '256.00'],
+      [5,    3, '125.00'],
+      [-10,  5, '-100000.00'],
+      [-10,  1, '-10.00'],
+      [-10,  0, '1.00'],
+      [2,   -2, '0.25'],
+    ];
+
+    for (const cas of cases) {
+
+      it(`${cas[0]} ** ${cas[1]} = ${cas[2]}`, () => {
+
+        const x = new Money(cas[0], 'CAD');
+        expect(x.pow(cas[1]).toFixed(2)).to.equal(cas[2]);
+
+      });
+
+    }
+
+  });
+
   describe('abs', () => {
 
     const cases = [

From edb713903af4eb1234e77dc3051f4f5c1d7992b9 Mon Sep 17 00:00:00 2001
From: Evert Pot <me@evertpot.com>
Date: Sat, 1 Aug 2020 16:44:37 -0400
Subject: [PATCH 2/4] Remove redundant branches

---
 src/money.ts | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/src/money.ts b/src/money.ts
index e6b4844..a4cbc1a 100644
--- a/src/money.ts
+++ b/src/money.ts
@@ -121,11 +121,7 @@ export class Money {
       throw new Error('You can currently only use pow() with whole numbers');
     }
 
-    if (exponent===1) {
-      return this;
-    } else if (exponent === 0) {
-      return new Money(1, this.currency);
-    } else if (exponent > 1) {
+    if (exponent > 1) {
       let base:Money = this;
       for(let i = 1; i < exponent; i++) {
         base = base.multiply(this);

From a0253c8e73aafb8a62425f86dd28ceea5b72ef69 Mon Sep 17 00:00:00 2001
From: Evert Pot <me@evertpot.com>
Date: Sat, 1 Aug 2020 16:57:55 -0400
Subject: [PATCH 3/4] Fast version

---
 src/money.ts | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/src/money.ts b/src/money.ts
index a4cbc1a..c22ce11 100644
--- a/src/money.ts
+++ b/src/money.ts
@@ -115,19 +115,23 @@ export class Money {
    *
    * pow currently only supports whole numbers.
    */
-  pow(exponent: number): Money {
+  pow(exponent: number | bigint): Money {
 
-    if (!Number.isInteger(exponent)) {
+    if (typeof exponent === 'number' && !Number.isInteger(exponent)) {
       throw new Error('You can currently only use pow() with whole numbers');
     }
 
     if (exponent > 1) {
-      let base:Money = this;
-      for(let i = 1; i < exponent; i++) {
-        base = base.multiply(this);
-      }
-      return base;
+      const resultBig = this.value ** BigInt(exponent);
+      return Money.fromSource(
+        divide(resultBig, PRECISION_M ** (BigInt(exponent)-1n), this.round),
+        this.currency,
+        this.round
+      );
     } else {
+      // This handles the 0, 1 and negative exponent cases.
+      // This uses an iterative approach and is therefore not going to super
+      // fast.
       let base:Money = this;
       for(let i = 1; i > exponent; i--) {
         base = base.divide(this);

From fb9649a7dae0811d0fba0343dfc80825cc7b0b2c Mon Sep 17 00:00:00 2001
From: Evert Pot <me@evertpot.com>
Date: Sat, 1 Aug 2020 17:00:27 -0400
Subject: [PATCH 4/4] Update docs

---
 CHANGELOG.md | 6 ++++++
 readme.md    | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a644503..80fa6ae 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,12 @@
 Changelog
 =========
 
+1.2.0 (2020-08-01)
+------------------
+
+* Added `pow()` operation.
+
+
 1.1.1 (2020-02-02)
 ------------------
 
diff --git a/readme.md b/readme.md
index b78e0c2..1439d7c 100644
--- a/readme.md
+++ b/readme.md
@@ -118,6 +118,9 @@ const result = new Money(10).divide(3);
 
 // Multiplication
 const result = new Money('2000').multiply('1.25');
+
+// Powers
+const result = new Money(2).pow(8);
 ```
 
 ### Comparing objects