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import { gcd } from ".";
/** Serializable representation of a ratio. */
export type RatioData = [numerator: number, denominator: number];
/** Representation of a ratio for performing fractional artithmetic. */
export default class Ratio {
readonly #numerator: number;
readonly #denominator: number;
get numerator(): number {
return this.#numerator;
}
get denominator(): number {
return this.#denominator;
}
constructor(numerator: number, denominator: number) {
if (!Number.isInteger(numerator) || !Number.isInteger(denominator)) {
throw new TypeError(
`Ratio must have integer parts: ${numerator} / ${denominator}`,
);
}
if (denominator === 0) {
throw new RangeError("Ratio demnominator cannot be zero");
}
const divisor = gcd(numerator, denominator);
this.#numerator = numerator / divisor;
this.#denominator = denominator / divisor;
}
multiplyRatio(other: Ratio): Ratio {
return new Ratio(
this.numerator * other.numerator,
this.denominator * other.denominator,
);
}
divideRatio(other: Ratio): Ratio {
return new Ratio(
this.numerator * other.denominator,
this.denominator * other.numerator,
);
}
add(other: Ratio): Ratio {
return new Ratio(
this.numerator * other.denominator + other.numerator * this.denominator,
this.denominator * other.denominator,
);
}
subtract(other: Ratio): Ratio {
return new Ratio(
this.numerator * other.denominator - other.numerator * this.denominator,
this.denominator * other.denominator,
);
}
compare(other: Ratio): number {
const left = this.numerator * other.denominator;
const right = other.numerator * this.denominator;
return left < right ? -1 : left > right ? 1 : 0;
}
equals(other: Ratio): boolean {
return this.compare(other) === 0;
}
toNumber(): number {
return this.numerator / this.denominator;
}
toString(): string {
return `${this.numerator}/${this.denominator}`;
}
[Symbol.for("nodejs.util.inspect.custom")](): string {
return `Ratio { ${this.numerator}/${this.denominator} }`;
}
static fromInteger(n: number): Ratio {
return new Ratio(n, 1);
}
toData(): RatioData {
return [this.numerator, this.denominator];
}
static fromData(ratio: RatioData): Ratio {
return new Ratio(ratio[0], ratio[1]);
}
static min(...ratios: Ratio[]): Ratio {
return ratios.reduce((a, b) => (a.compare(b) <= 0 ? a : b));
}
static max(...ratios: Ratio[]): Ratio {
return ratios.reduce((a, b) => (a.compare(b) >= 0 ? a : b));
}
}
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