postcss-calc/src/lib/simplify/inverse-trig.js

PostCSS plugin to reduce calc()

// §10.4 — asin/acos/atan. Bare <number> in, <angle> in degrees out.

import { num, dim, call } from '../node.js';

/** @typedef {import('../node.js').Node} Node */

const INVERSE_TRIG_OPS = /** @type {const} */ ({
  asin: Math.asin,
  acos: Math.acos,
  atan: Math.atan,
});

/**
 * @param {'asin' | 'acos' | 'atan'} name
 * @param {Node[]} args
 * @return {Node}
 */
function simplifyInverseTrig(name, args) {
  if (args.length !== 1) {
    return call(name, args);
  }
  const a = args[0];
  if (a.type !== 'Num') {
    return call(name, args);
  }
  const radians = INVERSE_TRIG_OPS[name](a.value);
  if (Number.isNaN(radians)) {
    return num(Number.NaN);
  }
  return dim((radians * 180) / Math.PI, 'deg');
}

export { simplifyInverseTrig };