From 6ce9d30c0fbf9a2d4f0214610ff50b521ead0e30 Mon Sep 17 00:00:00 2001
From: Frank Stokes <frank@wearereasonablepeople.com>
Date: Fri, 8 Oct 2021 11:19:50 +0200
Subject: [PATCH] Implement Symbol.toPrimitive

---
 decimal.js                  |  8 ++++++++
 test/modules/toPrimitive.js | 23 +++++++++++++++++++++++
 test/test.js                |  3 ++-
 3 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 test/modules/toPrimitive.js

diff --git a/decimal.js b/decimal.js
index aeb59dc..d2100c0 100644
--- a/decimal.js
+++ b/decimal.js
@@ -2467,6 +2467,14 @@
     return x.isNeg() ? '-' + str : str;
   };
 
+  /*
+   * The toPrimitive method is used when attempting to perform comparison operations.
+   * This implementation provides a sensible and user-expected implementation of how
+   * a Decimal should be transformed into a comparable number
+   */
+  P[Symbol.toPrimitive] = function () {
+    return Number(this.toString());
+  };
 
   // Helper functions for Decimal.prototype (P) and/or Decimal methods, and their callers.
 
diff --git a/test/modules/toPrimitive.js b/test/modules/toPrimitive.js
new file mode 100644
index 0000000..bcd148f
--- /dev/null
+++ b/test/modules/toPrimitive.js
@@ -0,0 +1,23 @@
+if (typeof T === 'undefined') require('../setup');
+
+T('Symbol.toPrimitive', function () {
+
+  function D(v) { return new Decimal(v); }
+
+  Decimal.config({
+    precision: 20,
+    rounding: 4,
+    toExpNeg: -9e15,
+    toExpPos: 9e15,
+    minE: -9e15,
+    maxE: 9e15
+  });
+
+  T.assert(D('1') < D('2'));
+  T.assert(D('100') > D('2'));
+  T.assert(D('-435435.232') < D('2.09802'));
+  T.assert(D('-1.987234') > D('-2.5473421'));
+  T.assert(D('10.3') >= D('10.3'));
+  T.assert(D('10.3') <= D('10.3'));
+});
+
diff --git a/test/test.js b/test/test.js
index 9758ea1..be1cc72 100644
--- a/test/test.js
+++ b/test/test.js
@@ -64,7 +64,8 @@ console.log('\n Testing decimal.js\n');
   'toSD',
   'toString',
   'trunc',
-  'valueOf'
+  'valueOf',
+  'toPrimitive',
 ]
 .forEach(function (module) {
   require('./modules/' + module);