fix: Fixed when both operands are zero

lib/decimal.js

@@ -28,6 +28,8 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 var DECIMAL_SEPARATOR = '.';
 
+import { DivisionByZeroError } from './exceptions.js';
+
 // Decimal
 var Decimal = function (num) {
   if (this === undefined) {
@@ -45,7 +47,24 @@ var Decimal = function (num) {
   this.internal = String(num);
   this.as_int = as_integer(this.internal);
 
+  // Helper to normalize zero values
+  this.normalizeZero = function () {
+    if (
+      this.internal === '0' ||
+      this.internal === '-0' ||
+      this.internal === '00' ||
+      this.internal === '000'
+    ) {
+      return '0';
+    }
+    return this.internal;
+  };
+
   this.add = function (target) {
+    if ((this.internal === '0' || this.internal === '-0') && (target === '0' || target === '-0')) {
+      return Decimal('0');
+    }
+
     var operands = [this, new Decimal(target)];
     operands.sort(function (x, y) {
       return x.as_int.exp - y.as_int.exp;
@@ -63,10 +82,17 @@ var Decimal = function (num) {
   };
 
   this.sub = function (target) {
+    if ((this.internal === '0' || this.internal === '-0') && (target === '0' || target === '-0')) {
+      return Decimal('0');
+    }
     return Decimal(this.add(target * -1));
   };
 
   this.mul = function (target) {
+    if ((this.internal === '0' || this.internal === '-0') && (target === '0' || target === '-0')) {
+      return Decimal('0');
+    }
+
     target = new Decimal(target);
     var result = String(this.as_int.value * target.as_int.value);
     var exp = this.as_int.exp + target.as_int.exp;
@@ -77,10 +103,14 @@ var Decimal = function (num) {
   this.div = function (target) {
     target = new Decimal(target);
 
+    if (target.internal === '0' || target.internal === '-0') {
+      throw new DivisionByZeroError('Division by zero');
+    }
+
     var smallest = Math.min(this.as_int.exp, target.as_int.exp);
 
-    var x = Decimal.mul(Math.pow(10, Decimal.abs(smallest).toNumber()), this);
-    var y = Decimal.mul(Math.pow(10, Decimal.abs(smallest).toNumber()), target);
+    var x = Decimal.mul(Math.pow(10, Decimal.abs(smallest)), this);
+    var y = Decimal.mul(Math.pow(10, Decimal.abs(smallest)), target);
 
     return Decimal(x / y);
   };
@@ -158,7 +188,7 @@ var Decimal = function (num) {
   };
 
   this.toString = function () {
-    return this.internal;
+    return this.normalizeZero();
   };
 
   this.toNumber = function () {
@@ -197,7 +227,6 @@ var as_integer = function (number) {
   };
 };
 
-// Helpers
 // Helpers
 var neg_exp = function (str, position, sign) {
   position = Decimal.abs(position);

lib/exceptions.js

@@ -0,0 +1,11 @@
+// Division by zero error
+
+function DivisionByZeroError(message) {
+  this.name = 'DivisionByZeroError';
+  this.message = message || 'Cannot divide by zero';
+}
+DivisionByZeroError.prototype = Object.create(Error.prototype);
+DivisionByZeroError.prototype.constructor = DivisionByZeroError;
+
+// Exports
+export { DivisionByZeroError };

tests/zero.js

@@ -0,0 +1,49 @@
+import { test } from 'node:test';
+import assert from 'node:assert';
+import Decimal from '../lib/decimal.js';
+import { DivisionByZeroError } from '../lib/exceptions.js';
+
+test('zero addition', function (t) {
+  assert.equal(Decimal('0').add('0').toString(), '0');
+  assert.equal(Decimal('-0').add('0').toString(), '0');
+  assert.equal(Decimal('0').add('-0').toString(), '0');
+  assert.equal(Decimal('-0').add('-0').toString(), '0');
+
+  // Static method
+  assert.equal(Decimal.add('0', '0').toString(), '0');
+  assert.equal(Decimal.add('-0', '0').toString(), '0');
+});
+
+test('zero subtraction', function (t) {
+  assert.equal(Decimal('0').sub('0').toString(), '0');
+  assert.equal(Decimal('-0').sub('0').toString(), '0');
+  assert.equal(Decimal('0').sub('-0').toString(), '0');
+  assert.equal(Decimal('-0').sub('-0').toString(), '0');
+
+  // Static method
+  assert.equal(Decimal.sub('0', '0').toString(), '0');
+  assert.equal(Decimal.sub('-0', '0').toString(), '0');
+});
+
+test('zero multiplication', function (t) {
+  assert.equal(Decimal('0').mul('0').toString(), '0');
+  assert.equal(Decimal('-0').mul('0').toString(), '0');
+  assert.equal(Decimal('0').mul('-0').toString(), '0');
+  assert.equal(Decimal('-0').mul('-0').toString(), '0');
+
+  // Static method
+  assert.equal(Decimal.mul('0', '0').toString(), '0');
+  assert.equal(Decimal.mul('-0', '0').toString(), '0');
+});
+
+test('zero division', function (t) {
+  // Division by zero should throw an error
+  assert.throws(() => Decimal('0').div('0'), DivisionByZeroError);
+  assert.throws(() => Decimal('-0').div('0'), DivisionByZeroError);
+  assert.throws(() => Decimal('0').div('-0'), DivisionByZeroError);
+  assert.throws(() => Decimal('-0').div('-0'), DivisionByZeroError);
+
+  // Static method
+  assert.throws(() => Decimal.div('0', '0'), DivisionByZeroError);
+  assert.throws(() => Decimal.div('-0', '0'), DivisionByZeroError);
+});