@fractorysolutions/safe-units/src/unit/trig.ts

Type-safe TypeScript units of measure

import { Exponent } from "../exponent";
import { GenericMeasure } from "../measure/genericMeasure";
import { Measure } from "../measure/numberMeasure";
import { radians } from "./base";
import { Length, PlaneAngle } from "./quantities";

/**
 * `Math.acos` for `number` measures.
 * @param x a dimensionless value
 * @returns an angle
 */
export const acos = wrapInverseTrigFn(Math.acos);

/**
 * `Math.asin` for `number` measures.
 * @param x a dimensionless value
 * @returns an angle
 */
export const asin = wrapInverseTrigFn(Math.asin);

/**
 * `Math.atan` for `number` measures.
 * @param x a dimensionless value
 * @returns an angle
 */
export const atan = wrapInverseTrigFn(Math.atan);

/**
 * `Math.cos` for `number` measures.
 * @param x an angle
 * @returns a dimensionless value
 */
export const cos = wrapTrigFn(Math.cos);

/**
 * `Math.sin` for `number` measures.
 * @param x an angle
 * @returns a dimensionless value
 */
export const sin = wrapTrigFn(Math.sin);

/**
 * `Math.tan` for `number` measures.
 * @param x an angle
 * @returns a dimensionless value
 */
export const tan = wrapTrigFn(Math.tan);

/**
 * `Math.atan2` for `number` measures.
 * @param x a length
 * @param y a length
 * @returns an angle
 */
export function atan2(y: Length, x: Length): PlaneAngle {
  return Measure.of(Math.atan2(y.value, x.value), radians);
}

type Dimensionless = GenericMeasure<
  number,
  Record<never, Exponent | undefined>
>;

function wrapTrigFn(
  f: (x: number) => number,
): (angle: PlaneAngle) => Dimensionless {
  return (angle) => Measure.dimensionless(f(angle.value));
}

function wrapInverseTrigFn(
  f: (x: number) => number,
): (angle: Dimensionless) => PlaneAngle {
  return (angle) => Measure.of(f(angle.value), radians);
}