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math: Add Decimal.multiply method and tests

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willclarktech 2020-08-18 16:07:15 +01:00
parent 04f8e06771
commit b94825f806
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3 changed files with 59 additions and 0 deletions
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41
packages/math/src/decimal.spec.ts
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@ -211,6 +211,47 @@ describe("Decimal", () => {
});
});
describe("multiply", () => {
it("returns correct values", () => {
const zero = Decimal.fromUserInput("0", 5);
expect(zero.multiply(Decimal.fromUserInput("0", 5)).toString()).toEqual("0");
expect(zero.multiply(Decimal.fromUserInput("1", 5)).toString()).toEqual("0");
expect(zero.multiply(Decimal.fromUserInput("2", 5)).toString()).toEqual("0");
expect(zero.multiply(Decimal.fromUserInput("2.8", 5)).toString()).toEqual("0");
expect(zero.multiply(Decimal.fromUserInput("0.12345", 5)).toString()).toEqual("0");
const one = Decimal.fromUserInput("1", 5);
expect(one.multiply(Decimal.fromUserInput("0", 5)).toString()).toEqual("0");
expect(one.multiply(Decimal.fromUserInput("1", 5)).toString()).toEqual("1");
expect(one.multiply(Decimal.fromUserInput("2", 5)).toString()).toEqual("2");
expect(one.multiply(Decimal.fromUserInput("2.8", 5)).toString()).toEqual("2.8");
expect(one.multiply(Decimal.fromUserInput("0.12345", 5)).toString()).toEqual("0.12345");
const oneDotFive = Decimal.fromUserInput("1.5", 5);
expect(oneDotFive.multiply(Decimal.fromUserInput("0", 5)).toString()).toEqual("0");
expect(oneDotFive.multiply(Decimal.fromUserInput("1", 5)).toString()).toEqual("1.5");
expect(oneDotFive.multiply(Decimal.fromUserInput("2", 5)).toString()).toEqual("3");
expect(oneDotFive.multiply(Decimal.fromUserInput("2.8", 5)).toString()).toEqual("4.2");
expect(oneDotFive.multiply(Decimal.fromUserInput("0.12345", 5)).toString()).toEqual("0.18517");
// original value remain unchanged
expect(zero.toString()).toEqual("0");
expect(one.toString()).toEqual("1");
expect(oneDotFive.toString()).toEqual("1.5");
});
it("throws for different fractional digits", () => {
const zero = Decimal.fromUserInput("0", 5);
expect(() => zero.multiply(Decimal.fromUserInput("1", 1))).toThrowError(/do not match/i);
expect(() => zero.multiply(Decimal.fromUserInput("1", 2))).toThrowError(/do not match/i);
expect(() => zero.multiply(Decimal.fromUserInput("1", 3))).toThrowError(/do not match/i);
expect(() => zero.multiply(Decimal.fromUserInput("1", 4))).toThrowError(/do not match/i);
expect(() => zero.multiply(Decimal.fromUserInput("1", 6))).toThrowError(/do not match/i);
expect(() => zero.multiply(Decimal.fromUserInput("1", 7))).toThrowError(/do not match/i);
});
});
describe("equals", () => {
it("returns correct values", () => {
const zero = Decimal.fromUserInput("0", 5);

12
packages/math/src/decimal.ts
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@ -124,6 +124,18 @@ export class Decimal {
return new Decimal(sum.toString(), this.fractionalDigits);
}
/**
* a.multiply(b) returns a*b.
*
* Both values need to have the same fractional digits.
*/
public multiply(b: Decimal): Decimal {
if (this.fractionalDigits !== b.fractionalDigits) throw new Error("Fractional digits do not match");
const factor = new BN(10).pow(new BN(this.data.fractionalDigits));
const product = this.data.atomics.mul(new BN(b.atomics)).div(factor);
return new Decimal(product.toString(), this.fractionalDigits);
}
public equals(b: Decimal): boolean {
return Decimal.compare(this, b) === 0;
}

6
packages/math/types/decimal.d.ts vendored
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@ -24,6 +24,12 @@ export declare class Decimal {
* Both values need to have the same fractional digits.
*/
plus(b: Decimal): Decimal;
/**
* a.multiply(b) returns a*b.
*
* Both values need to have the same fractional digits.
*/
multiply(b: Decimal): Decimal;
equals(b: Decimal): boolean;
isLessThan(b: Decimal): boolean;
isLessThanOrEqual(b: Decimal): boolean;