Add Decimal.zero and Decimal.one

CHANGELOG.md

@@ -6,6 +6,12 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Added
+
+- @cosmjs/math: Add `Decimal.zero` and `Decimal.one` ([#1110]).
+
+[#1110]: https://github.com/cosmos/cosmjs/issues/1110
+
 ## [0.28.3] - 2022-04-11
 
 ### Added

packages/math/src/decimal.spec.ts

@@ -133,6 +133,50 @@ describe("Decimal", () => {
     });
   });
 
+  describe("zero", () => {
+    it("works", () => {
+      expect(Decimal.zero(0).toString()).toEqual("0");
+      expect(Decimal.zero(1).toString()).toEqual("0");
+      expect(Decimal.zero(2).toString()).toEqual("0");
+      expect(Decimal.zero(30).toString()).toEqual("0");
+
+      expect(Decimal.zero(0).fractionalDigits).toEqual(0);
+      expect(Decimal.zero(1).fractionalDigits).toEqual(1);
+      expect(Decimal.zero(2).fractionalDigits).toEqual(2);
+      expect(Decimal.zero(30).fractionalDigits).toEqual(30);
+
+      expect(Decimal.zero(0).atomics).toEqual("0");
+      expect(Decimal.zero(1).atomics).toEqual("0");
+      expect(Decimal.zero(2).atomics).toEqual("0");
+      expect(Decimal.zero(30).atomics).toEqual("0");
+
+      expect(() => Decimal.zero(NaN)).toThrowError(/Fractional digits is not an integer/i);
+      expect(() => Decimal.zero(1.2)).toThrowError(/Fractional digits is not an integer/i);
+    });
+  });
+
+  describe("one", () => {
+    it("works", () => {
+      expect(Decimal.one(0).toString()).toEqual("1");
+      expect(Decimal.one(1).toString()).toEqual("1");
+      expect(Decimal.one(2).toString()).toEqual("1");
+      expect(Decimal.one(30).toString()).toEqual("1");
+
+      expect(Decimal.one(0).fractionalDigits).toEqual(0);
+      expect(Decimal.one(1).fractionalDigits).toEqual(1);
+      expect(Decimal.one(2).fractionalDigits).toEqual(2);
+      expect(Decimal.one(30).fractionalDigits).toEqual(30);
+
+      expect(Decimal.one(0).atomics).toEqual("1");
+      expect(Decimal.one(1).atomics).toEqual("10");
+      expect(Decimal.one(2).atomics).toEqual("100");
+      expect(Decimal.one(30).atomics).toEqual("1000000000000000000000000000000");
+
+      expect(() => Decimal.one(NaN)).toThrowError(/Fractional digits is not an integer/i);
+      expect(() => Decimal.one(1.2)).toThrowError(/Fractional digits is not an integer/i);
+    });
+  });
+
   describe("toString", () => {
     it("displays no decimal point for full numbers", () => {
       expect(Decimal.fromUserInput("44", 0).toString()).toEqual("44");

packages/math/src/decimal.ts

@@ -58,6 +58,28 @@ export class Decimal {
     return new Decimal(atomics, fractionalDigits);
   }
 
+  /**
+   * Creates a Decimal with value 0.0 and the given number of fractial digits.
+   *
+   * Fractional digits are not relevant for the value but needed to be able
+   * to perform arithmetic operations with other decimals.
+   */
+  public static zero(fractionalDigits: number): Decimal {
+    Decimal.verifyFractionalDigits(fractionalDigits);
+    return new Decimal("0", fractionalDigits);
+  }
+
+  /**
+   * Creates a Decimal with value 1.0 and the given number of fractial digits.
+   *
+   * Fractional digits are not relevant for the value but needed to be able
+   * to perform arithmetic operations with other decimals.
+   */
+  public static one(fractionalDigits: number): Decimal {
+    Decimal.verifyFractionalDigits(fractionalDigits);
+    return new Decimal("1" + "0".repeat(fractionalDigits), fractionalDigits);
+  }
+
   private static verifyFractionalDigits(fractionalDigits: number): void {
     if (!Number.isInteger(fractionalDigits)) throw new Error("Fractional digits is not an integer");
     if (fractionalDigits < 0) throw new Error("Fractional digits must not be negative");