Add neg(ation) (#103)

* Add neg(ation)

* Document change

CHANGELOG.md

@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [12.1.0] - 2024-04-11
+
+### Added
+
+-   New negation operator `neg`
+
 ## [12.0.0] - 2024-04-10
 
 ### Removed

src/decimal128.mts

@@ -1209,14 +1209,14 @@ export class Decimal128 {
 
         if (!this.isFinite) {
             if (this.isNegative) {
-                return this.negate();
+                return this.neg();
             }
 
             return this.clone();
         }
 
         if (this.isNegative) {
-            return this.negate();
+            return this.neg();
         }
 
         return this.clone();
@@ -1250,7 +1250,7 @@ export class Decimal128 {
         }
 
         if (this.isNegative && x.isNegative) {
-            return this.negate().add(x.negate(), opts).negate();
+            return this.neg().add(x.neg(), opts).neg();
         }
 
         let resultRat = Rational.add(this.rat, x.rat);
@@ -1290,11 +1290,11 @@ export class Decimal128 {
         }
 
         if (!x.isFinite) {
-            return x.negate();
+            return x.neg();
         }
 
         if (x.isNegative) {
-            return this.add(x.negate());
+            return this.add(x.neg());
         }
 
         let rendered = Rational.subtract(this.rat, x.rat).toDecimalPlaces(
@@ -1348,11 +1348,11 @@ export class Decimal128 {
         }
 
         if (this.isNegative) {
-            return this.negate().multiply(x).negate();
+            return this.neg().multiply(x).neg();
         }
 
         if (x.isNegative) {
-            return this.multiply(x.negate()).negate();
+            return this.multiply(x.neg()).neg();
         }
 
         let resultRat = Rational.multiply(this.rat, x.rat);
@@ -1413,11 +1413,11 @@ export class Decimal128 {
         }
 
         if (this.isNegative) {
-            return this.negate().divide(x).negate();
+            return this.neg().divide(x).neg();
         }
 
         if (x.isNegative) {
-            return this.divide(x.negate()).negate();
+            return this.divide(x.neg()).neg();
         }
 
         let adjust = 0;
@@ -1520,7 +1520,7 @@ export class Decimal128 {
         );
     }
 
-    private negate(): Decimal128 {
+    neg(): Decimal128 {
         let s = this.toString({ normalize: false });
 
         if (s.match(/^-/)) {
@@ -1543,11 +1543,11 @@ export class Decimal128 {
         }
 
         if (this.isNegative) {
-            return this.negate().remainder(d).negate();
+            return this.neg().remainder(d).neg();
         }
 
         if (d.isNegative) {
-            return this.remainder(d.negate());
+            return this.remainder(d.neg());
         }
 
         if (!this.isFinite) {

tests/neg.test.js

@@ -0,0 +1,52 @@
+import { Decimal128 } from "../src/decimal128.mjs";
+
+const MAX_SIGNIFICANT_DIGITS = 34;
+const bigDigits = "9".repeat(MAX_SIGNIFICANT_DIGITS);
+
+const zero = new Decimal128("0");
+const minusZero = new Decimal128("-0");
+const one = new Decimal128("1");
+const minusOne = new Decimal128("-1");
+const two = new Decimal128("2");
+
+describe("neg", () => {
+    test("minus zero", () => {
+        expect(new Decimal128("-0").neg().toString()).toStrictEqual("0");
+    });
+    test("zero", () => {
+        expect(new Decimal128("0").neg().toString()).toStrictEqual("-0");
+    });
+    test("NaN", () => {
+        expect(new Decimal128("NaN").neg().toString()).toStrictEqual("NaN");
+    });
+    test("negative number", () => {
+        expect(new Decimal128("-42.51").neg().toString()).toStrictEqual(
+            "42.51"
+        );
+    });
+    test("positive number", () => {
+        expect(new Decimal128("42.51").neg().toString()).toStrictEqual(
+            "-42.51"
+        );
+    });
+    test("preserve trailing zeros", () => {
+        expect(
+            new Decimal128("-42.510").neg().toString({ normalize: false })
+        ).toStrictEqual("42.510");
+    });
+    test("-Infinity", () => {
+        expect(new Decimal128("-Infinity").neg().toString()).toStrictEqual(
+            "Infinity"
+        );
+    });
+    test("Infinity", () => {
+        expect(new Decimal128("Infinity").neg().toString()).toStrictEqual(
+            "-Infinity"
+        );
+    });
+    test("limit of digits", () => {
+        expect(new Decimal128("-" + bigDigits).neg().toString()).toStrictEqual(
+            bigDigits
+        );
+    });
+});