source: node_modules/d3-scale/src/radial.js@ e4c61dd

import continuous from "./continuous.js";
import {initRange} from "./init.js";
import {linearish} from "./linear.js";
import number from "./number.js";

function square(x) {
  return Math.sign(x) * x * x;
}

function unsquare(x) {
  return Math.sign(x) * Math.sqrt(Math.abs(x));
}

export default function radial() {
  var squared = continuous(),
      range = [0, 1],
      round = false,
      unknown;

  function scale(x) {
    var y = unsquare(squared(x));
    return isNaN(y) ? unknown : round ? Math.round(y) : y;
  }

  scale.invert = function(y) {
    return squared.invert(square(y));
  };

  scale.domain = function(_) {
    return arguments.length ? (squared.domain(_), scale) : squared.domain();
  };

  scale.range = function(_) {
    return arguments.length ? (squared.range((range = Array.from(_, number)).map(square)), scale) : range.slice();
  };

  scale.rangeRound = function(_) {
    return scale.range(_).round(true);
  };

  scale.round = function(_) {
    return arguments.length ? (round = !!_, scale) : round;
  };

  scale.clamp = function(_) {
    return arguments.length ? (squared.clamp(_), scale) : squared.clamp();
  };

  scale.unknown = function(_) {
    return arguments.length ? (unknown = _, scale) : unknown;
  };

  scale.copy = function() {
    return radial(squared.domain(), range)
        .round(round)
        .clamp(squared.clamp())
        .unknown(unknown);
  };

  initRange.apply(scale, arguments);

  return linearish(scale);
}