Index: node_modules/decimal.js-light/decimal.js
===================================================================
--- node_modules/decimal.js-light/decimal.js	(revision a762898ecd37a452c782821d4c2c4955c6ed2521)
+++ node_modules/decimal.js-light/decimal.js	(revision a762898ecd37a452c782821d4c2c4955c6ed2521)
@@ -0,0 +1,2014 @@
+/*! decimal.js-light v2.5.1 https://github.com/MikeMcl/decimal.js-light/LICENCE */
+;(function (globalScope) {
+  'use strict';
+
+
+  /*
+   *  decimal.js-light v2.5.1
+   *  An arbitrary-precision Decimal type for JavaScript.
+   *  https://github.com/MikeMcl/decimal.js-light
+   *  Copyright (c) 2020 Michael Mclaughlin <M8ch88l@gmail.com>
+   *  MIT Expat Licence
+   */
+
+
+  // -----------------------------------  EDITABLE DEFAULTS  ------------------------------------ //
+
+
+    // The limit on the value of `precision`, and on the value of the first argument to
+    // `toDecimalPlaces`, `toExponential`, `toFixed`, `toPrecision` and `toSignificantDigits`.
+  var MAX_DIGITS = 1e9,                        // 0 to 1e9
+
+
+    // The initial configuration properties of the Decimal constructor.
+    Decimal = {
+
+      // These values must be integers within the stated ranges (inclusive).
+      // Most of these values can be changed during run-time using `Decimal.config`.
+
+      // The maximum number of significant digits of the result of a calculation or base conversion.
+      // E.g. `Decimal.config({ precision: 20 });`
+      precision: 20,                         // 1 to MAX_DIGITS
+
+      // The rounding mode used by default by `toInteger`, `toDecimalPlaces`, `toExponential`,
+      // `toFixed`, `toPrecision` and `toSignificantDigits`.
+      //
+      // ROUND_UP         0 Away from zero.
+      // ROUND_DOWN       1 Towards zero.
+      // ROUND_CEIL       2 Towards +Infinity.
+      // ROUND_FLOOR      3 Towards -Infinity.
+      // ROUND_HALF_UP    4 Towards nearest neighbour. If equidistant, up.
+      // ROUND_HALF_DOWN  5 Towards nearest neighbour. If equidistant, down.
+      // ROUND_HALF_EVEN  6 Towards nearest neighbour. If equidistant, towards even neighbour.
+      // ROUND_HALF_CEIL  7 Towards nearest neighbour. If equidistant, towards +Infinity.
+      // ROUND_HALF_FLOOR 8 Towards nearest neighbour. If equidistant, towards -Infinity.
+      //
+      // E.g.
+      // `Decimal.rounding = 4;`
+      // `Decimal.rounding = Decimal.ROUND_HALF_UP;`
+      rounding: 4,                           // 0 to 8
+
+      // The exponent value at and beneath which `toString` returns exponential notation.
+      // JavaScript numbers: -7
+      toExpNeg: -7,                          // 0 to -MAX_E
+
+      // The exponent value at and above which `toString` returns exponential notation.
+      // JavaScript numbers: 21
+      toExpPos:  21,                         // 0 to MAX_E
+
+      // The natural logarithm of 10.
+      // 115 digits
+      LN10: '2.302585092994045684017991454684364207601101488628772976033327900967572609677352480235997205089598298341967784042286'
+    },
+
+
+  // ----------------------------------- END OF EDITABLE DEFAULTS ------------------------------- //
+
+
+    external = true,
+
+    decimalError = '[DecimalError] ',
+    invalidArgument = decimalError + 'Invalid argument: ',
+    exponentOutOfRange = decimalError + 'Exponent out of range: ',
+
+    mathfloor = Math.floor,
+    mathpow = Math.pow,
+
+    isDecimal = /^(\d+(\.\d*)?|\.\d+)(e[+-]?\d+)?$/i,
+
+    ONE,
+    BASE = 1e7,
+    LOG_BASE = 7,
+    MAX_SAFE_INTEGER = 9007199254740991,
+    MAX_E = mathfloor(MAX_SAFE_INTEGER / LOG_BASE),    // 1286742750677284
+
+    // Decimal.prototype object
+    P = {};
+
+
+  // Decimal prototype methods
+
+
+  /*
+   *  absoluteValue                       abs
+   *  comparedTo                          cmp
+   *  decimalPlaces                       dp
+   *  dividedBy                           div
+   *  dividedToIntegerBy                  idiv
+   *  equals                              eq
+   *  exponent
+   *  greaterThan                         gt
+   *  greaterThanOrEqualTo                gte
+   *  isInteger                           isint
+   *  isNegative                          isneg
+   *  isPositive                          ispos
+   *  isZero
+   *  lessThan                            lt
+   *  lessThanOrEqualTo                   lte
+   *  logarithm                           log
+   *  minus                               sub
+   *  modulo                              mod
+   *  naturalExponential                  exp
+   *  naturalLogarithm                    ln
+   *  negated                             neg
+   *  plus                                add
+   *  precision                           sd
+   *  squareRoot                          sqrt
+   *  times                               mul
+   *  toDecimalPlaces                     todp
+   *  toExponential
+   *  toFixed
+   *  toInteger                           toint
+   *  toNumber
+   *  toPower                             pow
+   *  toPrecision
+   *  toSignificantDigits                 tosd
+   *  toString
+   *  valueOf                             val
+   */
+
+
+  /*
+   * Return a new Decimal whose value is the absolute value of this Decimal.
+   *
+   */
+  P.absoluteValue = P.abs = function () {
+    var x = new this.constructor(this);
+    if (x.s) x.s = 1;
+    return x;
+  };
+
+
+  /*
+   * Return
+   *   1    if the value of this Decimal is greater than the value of `y`,
+   *  -1    if the value of this Decimal is less than the value of `y`,
+   *   0    if they have the same value
+   *
+   */
+  P.comparedTo = P.cmp = function (y) {
+    var i, j, xdL, ydL,
+      x = this;
+
+    y = new x.constructor(y);
+
+    // Signs differ?
+    if (x.s !== y.s) return x.s || -y.s;
+
+    // Compare exponents.
+    if (x.e !== y.e) return x.e > y.e ^ x.s < 0 ? 1 : -1;
+
+    xdL = x.d.length;
+    ydL = y.d.length;
+
+    // Compare digit by digit.
+    for (i = 0, j = xdL < ydL ? xdL : ydL; i < j; ++i) {
+      if (x.d[i] !== y.d[i]) return x.d[i] > y.d[i] ^ x.s < 0 ? 1 : -1;
+    }
+
+    // Compare lengths.
+    return xdL === ydL ? 0 : xdL > ydL ^ x.s < 0 ? 1 : -1;
+  };
+
+
+  /*
+   * Return the number of decimal places of the value of this Decimal.
+   *
+   */
+  P.decimalPlaces = P.dp = function () {
+    var x = this,
+      w = x.d.length - 1,
+      dp = (w - x.e) * LOG_BASE;
+
+    // Subtract the number of trailing zeros of the last word.
+    w = x.d[w];
+    if (w) for (; w % 10 == 0; w /= 10) dp--;
+
+    return dp < 0 ? 0 : dp;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal divided by `y`, truncated to
+   * `precision` significant digits.
+   *
+   */
+  P.dividedBy = P.div = function (y) {
+    return divide(this, new this.constructor(y));
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the integer part of dividing the value of this Decimal
+   * by the value of `y`, truncated to `precision` significant digits.
+   *
+   */
+  P.dividedToIntegerBy = P.idiv = function (y) {
+    var x = this,
+      Ctor = x.constructor;
+    return round(divide(x, new Ctor(y), 0, 1), Ctor.precision);
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is equal to the value of `y`, otherwise return false.
+   *
+   */
+  P.equals = P.eq = function (y) {
+    return !this.cmp(y);
+  };
+
+
+  /*
+   * Return the (base 10) exponent value of this Decimal (this.e is the base 10000000 exponent).
+   *
+   */
+  P.exponent = function () {
+    return getBase10Exponent(this);
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is greater than the value of `y`, otherwise return
+   * false.
+   *
+   */
+  P.greaterThan = P.gt = function (y) {
+    return this.cmp(y) > 0;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is greater than or equal to the value of `y`,
+   * otherwise return false.
+   *
+   */
+  P.greaterThanOrEqualTo = P.gte = function (y) {
+    return this.cmp(y) >= 0;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is an integer, otherwise return false.
+   *
+   */
+  P.isInteger = P.isint = function () {
+    return this.e > this.d.length - 2;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is negative, otherwise return false.
+   *
+   */
+  P.isNegative = P.isneg = function () {
+    return this.s < 0;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is positive, otherwise return false.
+   *
+   */
+  P.isPositive = P.ispos = function () {
+    return this.s > 0;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is 0, otherwise return false.
+   *
+   */
+  P.isZero = function () {
+    return this.s === 0;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is less than `y`, otherwise return false.
+   *
+   */
+  P.lessThan = P.lt = function (y) {
+    return this.cmp(y) < 0;
+  };
+
+
+  /*
+   * Return true if the value of this Decimal is less than or equal to `y`, otherwise return false.
+   *
+   */
+  P.lessThanOrEqualTo = P.lte = function (y) {
+    return this.cmp(y) < 1;
+  };
+
+
+  /*
+   * Return the logarithm of the value of this Decimal to the specified base, truncated to
+   * `precision` significant digits.
+   *
+   * If no base is specified, return log[10](x).
+   *
+   * log[base](x) = ln(x) / ln(base)
+   *
+   * The maximum error of the result is 1 ulp (unit in the last place).
+   *
+   * [base] {number|string|Decimal} The base of the logarithm.
+   *
+   */
+  P.logarithm = P.log = function (base) {
+    var r,
+      x = this,
+      Ctor = x.constructor,
+      pr = Ctor.precision,
+      wpr = pr + 5;
+
+    // Default base is 10.
+    if (base === void 0) {
+      base = new Ctor(10);
+    } else {
+      base = new Ctor(base);
+
+      // log[-b](x) = NaN
+      // log[0](x)  = NaN
+      // log[1](x)  = NaN
+      if (base.s < 1 || base.eq(ONE)) throw Error(decimalError + 'NaN');
+    }
+
+    // log[b](-x) = NaN
+    // log[b](0) = -Infinity
+    if (x.s < 1) throw Error(decimalError + (x.s ? 'NaN' : '-Infinity'));
+
+    // log[b](1) = 0
+    if (x.eq(ONE)) return new Ctor(0);
+
+    external = false;
+    r = divide(ln(x, wpr), ln(base, wpr), wpr);
+    external = true;
+
+    return round(r, pr);
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal minus `y`, truncated to
+   * `precision` significant digits.
+   *
+   */
+  P.minus = P.sub = function (y) {
+    var x = this;
+    y = new x.constructor(y);
+    return x.s == y.s ? subtract(x, y) : add(x, (y.s = -y.s, y));
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal modulo `y`, truncated to
+   * `precision` significant digits.
+   *
+   */
+  P.modulo = P.mod = function (y) {
+    var q,
+      x = this,
+      Ctor = x.constructor,
+      pr = Ctor.precision;
+
+    y = new Ctor(y);
+
+    // x % 0 = NaN
+    if (!y.s) throw Error(decimalError + 'NaN');
+
+    // Return x if x is 0.
+    if (!x.s) return round(new Ctor(x), pr);
+
+    // Prevent rounding of intermediate calculations.
+    external = false;
+    q = divide(x, y, 0, 1).times(y);
+    external = true;
+
+    return x.minus(q);
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the natural exponential of the value of this Decimal,
+   * i.e. the base e raised to the power the value of this Decimal, truncated to `precision`
+   * significant digits.
+   *
+   */
+  P.naturalExponential = P.exp = function () {
+    return exp(this);
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the natural logarithm of the value of this Decimal,
+   * truncated to `precision` significant digits.
+   *
+   */
+  P.naturalLogarithm = P.ln = function () {
+    return ln(this);
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal negated, i.e. as if multiplied by
+   * -1.
+   *
+   */
+  P.negated = P.neg = function () {
+    var x = new this.constructor(this);
+    x.s = -x.s || 0;
+    return x;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal plus `y`, truncated to
+   * `precision` significant digits.
+   *
+   */
+  P.plus = P.add = function (y) {
+    var x = this;
+    y = new x.constructor(y);
+    return x.s == y.s ? add(x, y) : subtract(x, (y.s = -y.s, y));
+  };
+
+
+  /*
+   * Return the number of significant digits of the value of this Decimal.
+   *
+   * [z] {boolean|number} Whether to count integer-part trailing zeros: true, false, 1 or 0.
+   *
+   */
+  P.precision = P.sd = function (z) {
+    var e, sd, w,
+      x = this;
+
+    if (z !== void 0 && z !== !!z && z !== 1 && z !== 0) throw Error(invalidArgument + z);
+
+    e = getBase10Exponent(x) + 1;
+    w = x.d.length - 1;
+    sd = w * LOG_BASE + 1;
+    w = x.d[w];
+
+    // If non-zero...
+    if (w) {
+
+      // Subtract the number of trailing zeros of the last word.
+      for (; w % 10 == 0; w /= 10) sd--;
+
+      // Add the number of digits of the first word.
+      for (w = x.d[0]; w >= 10; w /= 10) sd++;
+    }
+
+    return z && e > sd ? e : sd;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the square root of this Decimal, truncated to `precision`
+   * significant digits.
+   *
+   */
+  P.squareRoot = P.sqrt = function () {
+    var e, n, pr, r, s, t, wpr,
+      x = this,
+      Ctor = x.constructor;
+
+    // Negative or zero?
+    if (x.s < 1) {
+      if (!x.s) return new Ctor(0);
+
+      // sqrt(-x) = NaN
+      throw Error(decimalError + 'NaN');
+    }
+
+    e = getBase10Exponent(x);
+    external = false;
+
+    // Initial estimate.
+    s = Math.sqrt(+x);
+
+    // Math.sqrt underflow/overflow?
+    // Pass x to Math.sqrt as integer, then adjust the exponent of the result.
+    if (s == 0 || s == 1 / 0) {
+      n = digitsToString(x.d);
+      if ((n.length + e) % 2 == 0) n += '0';
+      s = Math.sqrt(n);
+      e = mathfloor((e + 1) / 2) - (e < 0 || e % 2);
+
+      if (s == 1 / 0) {
+        n = '5e' + e;
+      } else {
+        n = s.toExponential();
+        n = n.slice(0, n.indexOf('e') + 1) + e;
+      }
+
+      r = new Ctor(n);
+    } else {
+      r = new Ctor(s.toString());
+    }
+
+    pr = Ctor.precision;
+    s = wpr = pr + 3;
+
+    // Newton-Raphson iteration.
+    for (;;) {
+      t = r;
+      r = t.plus(divide(x, t, wpr + 2)).times(0.5);
+
+      if (digitsToString(t.d).slice(0, wpr) === (n = digitsToString(r.d)).slice(0, wpr)) {
+        n = n.slice(wpr - 3, wpr + 1);
+
+        // The 4th rounding digit may be in error by -1 so if the 4 rounding digits are 9999 or
+        // 4999, i.e. approaching a rounding boundary, continue the iteration.
+        if (s == wpr && n == '4999') {
+
+          // On the first iteration only, check to see if rounding up gives the exact result as the
+          // nines may infinitely repeat.
+          round(t, pr + 1, 0);
+
+          if (t.times(t).eq(x)) {
+            r = t;
+            break;
+          }
+        } else if (n != '9999') {
+          break;
+        }
+
+        wpr += 4;
+      }
+    }
+
+    external = true;
+
+    return round(r, pr);
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal times `y`, truncated to
+   * `precision` significant digits.
+   *
+   */
+  P.times = P.mul = function (y) {
+    var carry, e, i, k, r, rL, t, xdL, ydL,
+      x = this,
+      Ctor = x.constructor,
+      xd = x.d,
+      yd = (y = new Ctor(y)).d;
+
+    // Return 0 if either is 0.
+    if (!x.s || !y.s) return new Ctor(0);
+
+    y.s *= x.s;
+    e = x.e + y.e;
+    xdL = xd.length;
+    ydL = yd.length;
+
+    // Ensure xd points to the longer array.
+    if (xdL < ydL) {
+      r = xd;
+      xd = yd;
+      yd = r;
+      rL = xdL;
+      xdL = ydL;
+      ydL = rL;
+    }
+
+    // Initialise the result array with zeros.
+    r = [];
+    rL = xdL + ydL;
+    for (i = rL; i--;) r.push(0);
+
+    // Multiply!
+    for (i = ydL; --i >= 0;) {
+      carry = 0;
+      for (k = xdL + i; k > i;) {
+        t = r[k] + yd[i] * xd[k - i - 1] + carry;
+        r[k--] = t % BASE | 0;
+        carry = t / BASE | 0;
+      }
+
+      r[k] = (r[k] + carry) % BASE | 0;
+    }
+
+    // Remove trailing zeros.
+    for (; !r[--rL];) r.pop();
+
+    if (carry) ++e;
+    else r.shift();
+
+    y.d = r;
+    y.e = e;
+
+    return external ? round(y, Ctor.precision) : y;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal rounded to a maximum of `dp`
+   * decimal places using rounding mode `rm` or `rounding` if `rm` is omitted.
+   *
+   * If `dp` is omitted, return a new Decimal whose value is the value of this Decimal.
+   *
+   * [dp] {number} Decimal places. Integer, 0 to MAX_DIGITS inclusive.
+   * [rm] {number} Rounding mode. Integer, 0 to 8 inclusive.
+   *
+   */
+  P.toDecimalPlaces = P.todp = function (dp, rm) {
+    var x = this,
+      Ctor = x.constructor;
+
+    x = new Ctor(x);
+    if (dp === void 0) return x;
+
+    checkInt32(dp, 0, MAX_DIGITS);
+
+    if (rm === void 0) rm = Ctor.rounding;
+    else checkInt32(rm, 0, 8);
+
+    return round(x, dp + getBase10Exponent(x) + 1, rm);
+  };
+
+
+  /*
+   * Return a string representing the value of this Decimal in exponential notation rounded to
+   * `dp` fixed decimal places using rounding mode `rounding`.
+   *
+   * [dp] {number} Decimal places. Integer, 0 to MAX_DIGITS inclusive.
+   * [rm] {number} Rounding mode. Integer, 0 to 8 inclusive.
+   *
+   */
+  P.toExponential = function (dp, rm) {
+    var str,
+      x = this,
+      Ctor = x.constructor;
+
+    if (dp === void 0) {
+      str = toString(x, true);
+    } else {
+      checkInt32(dp, 0, MAX_DIGITS);
+
+      if (rm === void 0) rm = Ctor.rounding;
+      else checkInt32(rm, 0, 8);
+
+      x = round(new Ctor(x), dp + 1, rm);
+      str = toString(x, true, dp + 1);
+    }
+
+    return str;
+  };
+
+
+  /*
+   * Return a string representing the value of this Decimal in normal (fixed-point) notation to
+   * `dp` fixed decimal places and rounded using rounding mode `rm` or `rounding` if `rm` is
+   * omitted.
+   *
+   * As with JavaScript numbers, (-0).toFixed(0) is '0', but e.g. (-0.00001).toFixed(0) is '-0'.
+   *
+   * [dp] {number} Decimal places. Integer, 0 to MAX_DIGITS inclusive.
+   * [rm] {number} Rounding mode. Integer, 0 to 8 inclusive.
+   *
+   * (-0).toFixed(0) is '0', but (-0.1).toFixed(0) is '-0'.
+   * (-0).toFixed(1) is '0.0', but (-0.01).toFixed(1) is '-0.0'.
+   * (-0).toFixed(3) is '0.000'.
+   * (-0.5).toFixed(0) is '-0'.
+   *
+   */
+  P.toFixed = function (dp, rm) {
+    var str, y,
+      x = this,
+      Ctor = x.constructor;
+
+    if (dp === void 0) return toString(x);
+
+    checkInt32(dp, 0, MAX_DIGITS);
+
+    if (rm === void 0) rm = Ctor.rounding;
+    else checkInt32(rm, 0, 8);
+
+    y = round(new Ctor(x), dp + getBase10Exponent(x) + 1, rm);
+    str = toString(y.abs(), false, dp + getBase10Exponent(y) + 1);
+
+    // To determine whether to add the minus sign look at the value before it was rounded,
+    // i.e. look at `x` rather than `y`.
+    return x.isneg() && !x.isZero() ? '-' + str : str;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal rounded to a whole number using
+   * rounding mode `rounding`.
+   *
+   */
+  P.toInteger = P.toint = function () {
+    var x = this,
+      Ctor = x.constructor;
+    return round(new Ctor(x), getBase10Exponent(x) + 1, Ctor.rounding);
+  };
+
+
+  /*
+   * Return the value of this Decimal converted to a number primitive.
+   *
+   */
+  P.toNumber = function () {
+    return +this;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal raised to the power `y`,
+   * truncated to `precision` significant digits.
+   *
+   * For non-integer or very large exponents pow(x, y) is calculated using
+   *
+   *   x^y = exp(y*ln(x))
+   *
+   * The maximum error is 1 ulp (unit in last place).
+   *
+   * y {number|string|Decimal} The power to which to raise this Decimal.
+   *
+   */
+  P.toPower = P.pow = function (y) {
+    var e, k, pr, r, sign, yIsInt,
+      x = this,
+      Ctor = x.constructor,
+      guard = 12,
+      yn = +(y = new Ctor(y));
+
+    // pow(x, 0) = 1
+    if (!y.s) return new Ctor(ONE);
+
+    x = new Ctor(x);
+
+    // pow(0, y > 0) = 0
+    // pow(0, y < 0) = Infinity
+    if (!x.s) {
+      if (y.s < 1) throw Error(decimalError + 'Infinity');
+      return x;
+    }
+
+    // pow(1, y) = 1
+    if (x.eq(ONE)) return x;
+
+    pr = Ctor.precision;
+
+    // pow(x, 1) = x
+    if (y.eq(ONE)) return round(x, pr);
+
+    e = y.e;
+    k = y.d.length - 1;
+    yIsInt = e >= k;
+    sign = x.s;
+
+    if (!yIsInt) {
+
+      // pow(x < 0, y non-integer) = NaN
+      if (sign < 0) throw Error(decimalError + 'NaN');
+
+    // If y is a small integer use the 'exponentiation by squaring' algorithm.
+    } else if ((k = yn < 0 ? -yn : yn) <= MAX_SAFE_INTEGER) {
+      r = new Ctor(ONE);
+
+      // Max k of 9007199254740991 takes 53 loop iterations.
+      // Maximum digits array length; leaves [28, 34] guard digits.
+      e = Math.ceil(pr / LOG_BASE + 4);
+
+      external = false;
+
+      for (;;) {
+        if (k % 2) {
+          r = r.times(x);
+          truncate(r.d, e);
+        }
+
+        k = mathfloor(k / 2);
+        if (k === 0) break;
+
+        x = x.times(x);
+        truncate(x.d, e);
+      }
+
+      external = true;
+
+      return y.s < 0 ? new Ctor(ONE).div(r) : round(r, pr);
+    }
+
+    // Result is negative if x is negative and the last digit of integer y is odd.
+    sign = sign < 0 && y.d[Math.max(e, k)] & 1 ? -1 : 1;
+
+    x.s = 1;
+    external = false;
+    r = y.times(ln(x, pr + guard));
+    external = true;
+    r = exp(r);
+    r.s = sign;
+
+    return r;
+  };
+
+
+  /*
+   * Return a string representing the value of this Decimal rounded to `sd` significant digits
+   * using rounding mode `rounding`.
+   *
+   * Return exponential notation if `sd` is less than the number of digits necessary to represent
+   * the integer part of the value in normal notation.
+   *
+   * [sd] {number} Significant digits. Integer, 1 to MAX_DIGITS inclusive.
+   * [rm] {number} Rounding mode. Integer, 0 to 8 inclusive.
+   *
+   */
+  P.toPrecision = function (sd, rm) {
+    var e, str,
+      x = this,
+      Ctor = x.constructor;
+
+    if (sd === void 0) {
+      e = getBase10Exponent(x);
+      str = toString(x, e <= Ctor.toExpNeg || e >= Ctor.toExpPos);
+    } else {
+      checkInt32(sd, 1, MAX_DIGITS);
+
+      if (rm === void 0) rm = Ctor.rounding;
+      else checkInt32(rm, 0, 8);
+
+      x = round(new Ctor(x), sd, rm);
+      e = getBase10Exponent(x);
+      str = toString(x, sd <= e || e <= Ctor.toExpNeg, sd);
+    }
+
+    return str;
+  };
+
+
+  /*
+   * Return a new Decimal whose value is the value of this Decimal rounded to a maximum of `sd`
+   * significant digits using rounding mode `rm`, or to `precision` and `rounding` respectively if
+   * omitted.
+   *
+   * [sd] {number} Significant digits. Integer, 1 to MAX_DIGITS inclusive.
+   * [rm] {number} Rounding mode. Integer, 0 to 8 inclusive.
+   *
+   */
+  P.toSignificantDigits = P.tosd = function (sd, rm) {
+    var x = this,
+      Ctor = x.constructor;
+
+    if (sd === void 0) {
+      sd = Ctor.precision;
+      rm = Ctor.rounding;
+    } else {
+      checkInt32(sd, 1, MAX_DIGITS);
+
+      if (rm === void 0) rm = Ctor.rounding;
+      else checkInt32(rm, 0, 8);
+    }
+
+    return round(new Ctor(x), sd, rm);
+  };
+
+
+  /*
+   * Return a string representing the value of this Decimal.
+   *
+   * Return exponential notation if this Decimal has a positive exponent equal to or greater than
+   * `toExpPos`, or a negative exponent equal to or less than `toExpNeg`.
+   *
+   */
+  P.toString = P.valueOf = P.val = P.toJSON = function () {
+    var x = this,
+      e = getBase10Exponent(x),
+      Ctor = x.constructor;
+
+    return toString(x, e <= Ctor.toExpNeg || e >= Ctor.toExpPos);
+  };
+
+
+  // Helper functions for Decimal.prototype (P) and/or Decimal methods, and their callers.
+
+
+  /*
+   *  add                 P.minus, P.plus
+   *  checkInt32          P.todp, P.toExponential, P.toFixed, P.toPrecision, P.tosd
+   *  digitsToString      P.log, P.sqrt, P.pow, toString, exp, ln
+   *  divide              P.div, P.idiv, P.log, P.mod, P.sqrt, exp, ln
+   *  exp                 P.exp, P.pow
+   *  getBase10Exponent   P.exponent, P.sd, P.toint, P.sqrt, P.todp, P.toFixed, P.toPrecision,
+   *                      P.toString, divide, round, toString, exp, ln
+   *  getLn10             P.log, ln
+   *  getZeroString       digitsToString, toString
+   *  ln                  P.log, P.ln, P.pow, exp
+   *  parseDecimal        Decimal
+   *  round               P.abs, P.idiv, P.log, P.minus, P.mod, P.neg, P.plus, P.toint, P.sqrt,
+   *                      P.times, P.todp, P.toExponential, P.toFixed, P.pow, P.toPrecision, P.tosd,
+   *                      divide, getLn10, exp, ln
+   *  subtract            P.minus, P.plus
+   *  toString            P.toExponential, P.toFixed, P.toPrecision, P.toString, P.valueOf
+   *  truncate            P.pow
+   *
+   *  Throws:             P.log, P.mod, P.sd, P.sqrt, P.pow,  checkInt32, divide, round,
+   *                      getLn10, exp, ln, parseDecimal, Decimal, config
+   */
+
+
+  function add(x, y) {
+    var carry, d, e, i, k, len, xd, yd,
+      Ctor = x.constructor,
+      pr = Ctor.precision;
+
+    // If either is zero...
+    if (!x.s || !y.s) {
+
+      // Return x if y is zero.
+      // Return y if y is non-zero.
+      if (!y.s) y = new Ctor(x);
+      return external ? round(y, pr) : y;
+    }
+
+    xd = x.d;
+    yd = y.d;
+
+    // x and y are finite, non-zero numbers with the same sign.
+
+    k = x.e;
+    e = y.e;
+    xd = xd.slice();
+    i = k - e;
+
+    // If base 1e7 exponents differ...
+    if (i) {
+      if (i < 0) {
+        d = xd;
+        i = -i;
+        len = yd.length;
+      } else {
+        d = yd;
+        e = k;
+        len = xd.length;
+      }
+
+      // Limit number of zeros prepended to max(ceil(pr / LOG_BASE), len) + 1.
+      k = Math.ceil(pr / LOG_BASE);
+      len = k > len ? k + 1 : len + 1;
+
+      if (i > len) {
+        i = len;
+        d.length = 1;
+      }
+
+      // Prepend zeros to equalise exponents. Note: Faster to use reverse then do unshifts.
+      d.reverse();
+      for (; i--;) d.push(0);
+      d.reverse();
+    }
+
+    len = xd.length;
+    i = yd.length;
+
+    // If yd is longer than xd, swap xd and yd so xd points to the longer array.
+    if (len - i < 0) {
+      i = len;
+      d = yd;
+      yd = xd;
+      xd = d;
+    }
+
+    // Only start adding at yd.length - 1 as the further digits of xd can be left as they are.
+    for (carry = 0; i;) {
+      carry = (xd[--i] = xd[i] + yd[i] + carry) / BASE | 0;
+      xd[i] %= BASE;
+    }
+
+    if (carry) {
+      xd.unshift(carry);
+      ++e;
+    }
+
+    // Remove trailing zeros.
+    // No need to check for zero, as +x + +y != 0 && -x + -y != 0
+    for (len = xd.length; xd[--len] == 0;) xd.pop();
+
+    y.d = xd;
+    y.e = e;
+
+    return external ? round(y, pr) : y;
+  }
+
+
+  function checkInt32(i, min, max) {
+    if (i !== ~~i || i < min || i > max) {
+      throw Error(invalidArgument + i);
+    }
+  }
+
+
+  function digitsToString(d) {
+    var i, k, ws,
+      indexOfLastWord = d.length - 1,
+      str = '',
+      w = d[0];
+
+    if (indexOfLastWord > 0) {
+      str += w;
+      for (i = 1; i < indexOfLastWord; i++) {
+        ws = d[i] + '';
+        k = LOG_BASE - ws.length;
+        if (k) str += getZeroString(k);
+        str += ws;
+      }
+
+      w = d[i];
+      ws = w + '';
+      k = LOG_BASE - ws.length;
+      if (k) str += getZeroString(k);
+    } else if (w === 0) {
+      return '0';
+    }
+
+    // Remove trailing zeros of last w.
+    for (; w % 10 === 0;) w /= 10;
+
+    return str + w;
+  }
+
+
+  var divide = (function () {
+
+    // Assumes non-zero x and k, and hence non-zero result.
+    function multiplyInteger(x, k) {
+      var temp,
+        carry = 0,
+        i = x.length;
+
+      for (x = x.slice(); i--;) {
+        temp = x[i] * k + carry;
+        x[i] = temp % BASE | 0;
+        carry = temp / BASE | 0;
+      }
+
+      if (carry) x.unshift(carry);
+
+      return x;
+    }
+
+    function compare(a, b, aL, bL) {
+      var i, r;
+
+      if (aL != bL) {
+        r = aL > bL ? 1 : -1;
+      } else {
+        for (i = r = 0; i < aL; i++) {
+          if (a[i] != b[i]) {
+            r = a[i] > b[i] ? 1 : -1;
+            break;
+          }
+        }
+      }
+
+      return r;
+    }
+
+    function subtract(a, b, aL) {
+      var i = 0;
+
+      // Subtract b from a.
+      for (; aL--;) {
+        a[aL] -= i;
+        i = a[aL] < b[aL] ? 1 : 0;
+        a[aL] = i * BASE + a[aL] - b[aL];
+      }
+
+      // Remove leading zeros.
+      for (; !a[0] && a.length > 1;) a.shift();
+    }
+
+    return function (x, y, pr, dp) {
+      var cmp, e, i, k, prod, prodL, q, qd, rem, remL, rem0, sd, t, xi, xL, yd0, yL, yz,
+        Ctor = x.constructor,
+        sign = x.s == y.s ? 1 : -1,
+        xd = x.d,
+        yd = y.d;
+
+      // Either 0?
+      if (!x.s) return new Ctor(x);
+      if (!y.s) throw Error(decimalError + 'Division by zero');
+
+      e = x.e - y.e;
+      yL = yd.length;
+      xL = xd.length;
+      q = new Ctor(sign);
+      qd = q.d = [];
+
+      // Result exponent may be one less than e.
+      for (i = 0; yd[i] == (xd[i] || 0); ) ++i;
+      if (yd[i] > (xd[i] || 0)) --e;
+
+      if (pr == null) {
+        sd = pr = Ctor.precision;
+      } else if (dp) {
+        sd = pr + (getBase10Exponent(x) - getBase10Exponent(y)) + 1;
+      } else {
+        sd = pr;
+      }
+
+      if (sd < 0) return new Ctor(0);
+
+      // Convert precision in number of base 10 digits to base 1e7 digits.
+      sd = sd / LOG_BASE + 2 | 0;
+      i = 0;
+
+      // divisor < 1e7
+      if (yL == 1) {
+        k = 0;
+        yd = yd[0];
+        sd++;
+
+        // k is the carry.
+        for (; (i < xL || k) && sd--; i++) {
+          t = k * BASE + (xd[i] || 0);
+          qd[i] = t / yd | 0;
+          k = t % yd | 0;
+        }
+
+      // divisor >= 1e7
+      } else {
+
+        // Normalise xd and yd so highest order digit of yd is >= BASE/2
+        k = BASE / (yd[0] + 1) | 0;
+
+        if (k > 1) {
+          yd = multiplyInteger(yd, k);
+          xd = multiplyInteger(xd, k);
+          yL = yd.length;
+          xL = xd.length;
+        }
+
+        xi = yL;
+        rem = xd.slice(0, yL);
+        remL = rem.length;
+
+        // Add zeros to make remainder as long as divisor.
+        for (; remL < yL;) rem[remL++] = 0;
+
+        yz = yd.slice();
+        yz.unshift(0);
+        yd0 = yd[0];
+
+        if (yd[1] >= BASE / 2) ++yd0;
+
+        do {
+          k = 0;
+
+          // Compare divisor and remainder.
+          cmp = compare(yd, rem, yL, remL);
+
+          // If divisor < remainder.
+          if (cmp < 0) {
+
+            // Calculate trial digit, k.
+            rem0 = rem[0];
+            if (yL != remL) rem0 = rem0 * BASE + (rem[1] || 0);
+
+            // k will be how many times the divisor goes into the current remainder.
+            k = rem0 / yd0 | 0;
+
+            //  Algorithm:
+            //  1. product = divisor * trial digit (k)
+            //  2. if product > remainder: product -= divisor, k--
+            //  3. remainder -= product
+            //  4. if product was < remainder at 2:
+            //    5. compare new remainder and divisor
+            //    6. If remainder > divisor: remainder -= divisor, k++
+
+            if (k > 1) {
+              if (k >= BASE) k = BASE - 1;
+
+              // product = divisor * trial digit.
+              prod = multiplyInteger(yd, k);
+              prodL = prod.length;
+              remL = rem.length;
+
+              // Compare product and remainder.
+              cmp = compare(prod, rem, prodL, remL);
+
+              // product > remainder.
+              if (cmp == 1) {
+                k--;
+
+                // Subtract divisor from product.
+                subtract(prod, yL < prodL ? yz : yd, prodL);
+              }
+            } else {
+
+              // cmp is -1.
+              // If k is 0, there is no need to compare yd and rem again below, so change cmp to 1
+              // to avoid it. If k is 1 there is a need to compare yd and rem again below.
+              if (k == 0) cmp = k = 1;
+              prod = yd.slice();
+            }
+
+            prodL = prod.length;
+            if (prodL < remL) prod.unshift(0);
+
+            // Subtract product from remainder.
+            subtract(rem, prod, remL);
+
+            // If product was < previous remainder.
+            if (cmp == -1) {
+              remL = rem.length;
+
+              // Compare divisor and new remainder.
+              cmp = compare(yd, rem, yL, remL);
+
+              // If divisor < new remainder, subtract divisor from remainder.
+              if (cmp < 1) {
+                k++;
+
+                // Subtract divisor from remainder.
+                subtract(rem, yL < remL ? yz : yd, remL);
+              }
+            }
+
+            remL = rem.length;
+          } else if (cmp === 0) {
+            k++;
+            rem = [0];
+          }    // if cmp === 1, k will be 0
+
+          // Add the next digit, k, to the result array.
+          qd[i++] = k;
+
+          // Update the remainder.
+          if (cmp && rem[0]) {
+            rem[remL++] = xd[xi] || 0;
+          } else {
+            rem = [xd[xi]];
+            remL = 1;
+          }
+
+        } while ((xi++ < xL || rem[0] !== void 0) && sd--);
+      }
+
+      // Leading zero?
+      if (!qd[0]) qd.shift();
+
+      q.e = e;
+
+      return round(q, dp ? pr + getBase10Exponent(q) + 1 : pr);
+    };
+  })();
+
+
+  /*
+   * Return a new Decimal whose value is the natural exponential of `x` truncated to `sd`
+   * significant digits.
+   *
+   * Taylor/Maclaurin series.
+   *
+   * exp(x) = x^0/0! + x^1/1! + x^2/2! + x^3/3! + ...
+   *
+   * Argument reduction:
+   *   Repeat x = x / 32, k += 5, until |x| < 0.1
+   *   exp(x) = exp(x / 2^k)^(2^k)
+   *
+   * Previously, the argument was initially reduced by
+   * exp(x) = exp(r) * 10^k  where r = x - k * ln10, k = floor(x / ln10)
+   * to first put r in the range [0, ln10], before dividing by 32 until |x| < 0.1, but this was
+   * found to be slower than just dividing repeatedly by 32 as above.
+   *
+   * (Math object integer min/max: Math.exp(709) = 8.2e+307, Math.exp(-745) = 5e-324)
+   *
+   *  exp(x) is non-terminating for any finite, non-zero x.
+   *
+   */
+  function exp(x, sd) {
+    var denominator, guard, pow, sum, t, wpr,
+      i = 0,
+      k = 0,
+      Ctor = x.constructor,
+      pr = Ctor.precision;
+
+    if (getBase10Exponent(x) > 16) throw Error(exponentOutOfRange + getBase10Exponent(x));
+
+    // exp(0) = 1
+    if (!x.s) return new Ctor(ONE);
+
+    if (sd == null) {
+      external = false;
+      wpr = pr;
+    } else {
+      wpr = sd;
+    }
+
+    t = new Ctor(0.03125);
+
+    while (x.abs().gte(0.1)) {
+      x = x.times(t);    // x = x / 2^5
+      k += 5;
+    }
+
+    // Estimate the precision increase necessary to ensure the first 4 rounding digits are correct.
+    guard = Math.log(mathpow(2, k)) / Math.LN10 * 2 + 5 | 0;
+    wpr += guard;
+    denominator = pow = sum = new Ctor(ONE);
+    Ctor.precision = wpr;
+
+    for (;;) {
+      pow = round(pow.times(x), wpr);
+      denominator = denominator.times(++i);
+      t = sum.plus(divide(pow, denominator, wpr));
+
+      if (digitsToString(t.d).slice(0, wpr) === digitsToString(sum.d).slice(0, wpr)) {
+        while (k--) sum = round(sum.times(sum), wpr);
+        Ctor.precision = pr;
+        return sd == null ? (external = true, round(sum, pr)) : sum;
+      }
+
+      sum = t;
+    }
+  }
+
+
+  // Calculate the base 10 exponent from the base 1e7 exponent.
+  function getBase10Exponent(x) {
+    var e = x.e * LOG_BASE,
+      w = x.d[0];
+
+    // Add the number of digits of the first word of the digits array.
+    for (; w >= 10; w /= 10) e++;
+    return e;
+  }
+
+
+  function getLn10(Ctor, sd, pr) {
+
+    if (sd > Ctor.LN10.sd()) {
+
+
+      // Reset global state in case the exception is caught.
+      external = true;
+      if (pr) Ctor.precision = pr;
+      throw Error(decimalError + 'LN10 precision limit exceeded');
+    }
+
+    return round(new Ctor(Ctor.LN10), sd);
+  }
+
+
+  function getZeroString(k) {
+    var zs = '';
+    for (; k--;) zs += '0';
+    return zs;
+  }
+
+
+  /*
+   * Return a new Decimal whose value is the natural logarithm of `x` truncated to `sd` significant
+   * digits.
+   *
+   *  ln(n) is non-terminating (n != 1)
+   *
+   */
+  function ln(y, sd) {
+    var c, c0, denominator, e, numerator, sum, t, wpr, x2,
+      n = 1,
+      guard = 10,
+      x = y,
+      xd = x.d,
+      Ctor = x.constructor,
+      pr = Ctor.precision;
+
+    // ln(-x) = NaN
+    // ln(0) = -Infinity
+    if (x.s < 1) throw Error(decimalError + (x.s ? 'NaN' : '-Infinity'));
+
+    // ln(1) = 0
+    if (x.eq(ONE)) return new Ctor(0);
+
+    if (sd == null) {
+      external = false;
+      wpr = pr;
+    } else {
+      wpr = sd;
+    }
+
+    if (x.eq(10)) {
+      if (sd == null) external = true;
+      return getLn10(Ctor, wpr);
+    }
+
+    wpr += guard;
+    Ctor.precision = wpr;
+    c = digitsToString(xd);
+    c0 = c.charAt(0);
+    e = getBase10Exponent(x);
+
+    if (Math.abs(e) < 1.5e15) {
+
+      // Argument reduction.
+      // The series converges faster the closer the argument is to 1, so using
+      // ln(a^b) = b * ln(a),   ln(a) = ln(a^b) / b
+      // multiply the argument by itself until the leading digits of the significand are 7, 8, 9,
+      // 10, 11, 12 or 13, recording the number of multiplications so the sum of the series can
+      // later be divided by this number, then separate out the power of 10 using
+      // ln(a*10^b) = ln(a) + b*ln(10).
+
+      // max n is 21 (gives 0.9, 1.0 or 1.1) (9e15 / 21 = 4.2e14).
+      //while (c0 < 9 && c0 != 1 || c0 == 1 && c.charAt(1) > 1) {
+      // max n is 6 (gives 0.7 - 1.3)
+      while (c0 < 7 && c0 != 1 || c0 == 1 && c.charAt(1) > 3) {
+        x = x.times(y);
+        c = digitsToString(x.d);
+        c0 = c.charAt(0);
+        n++;
+      }
+
+      e = getBase10Exponent(x);
+
+      if (c0 > 1) {
+        x = new Ctor('0.' + c);
+        e++;
+      } else {
+        x = new Ctor(c0 + '.' + c.slice(1));
+      }
+    } else {
+
+      // The argument reduction method above may result in overflow if the argument y is a massive
+      // number with exponent >= 1500000000000000 (9e15 / 6 = 1.5e15), so instead recall this
+      // function using ln(x*10^e) = ln(x) + e*ln(10).
+      t = getLn10(Ctor, wpr + 2, pr).times(e + '');
+      x = ln(new Ctor(c0 + '.' + c.slice(1)), wpr - guard).plus(t);
+
+      Ctor.precision = pr;
+      return sd == null ? (external = true, round(x, pr)) : x;
+    }
+
+    // x is reduced to a value near 1.
+
+    // Taylor series.
+    // ln(y) = ln((1 + x)/(1 - x)) = 2(x + x^3/3 + x^5/5 + x^7/7 + ...)
+    // where x = (y - 1)/(y + 1)    (|x| < 1)
+    sum = numerator = x = divide(x.minus(ONE), x.plus(ONE), wpr);
+    x2 = round(x.times(x), wpr);
+    denominator = 3;
+
+    for (;;) {
+      numerator = round(numerator.times(x2), wpr);
+      t = sum.plus(divide(numerator, new Ctor(denominator), wpr));
+
+      if (digitsToString(t.d).slice(0, wpr) === digitsToString(sum.d).slice(0, wpr)) {
+        sum = sum.times(2);
+
+        // Reverse the argument reduction.
+        if (e !== 0) sum = sum.plus(getLn10(Ctor, wpr + 2, pr).times(e + ''));
+        sum = divide(sum, new Ctor(n), wpr);
+
+        Ctor.precision = pr;
+        return sd == null ? (external = true, round(sum, pr)) : sum;
+      }
+
+      sum = t;
+      denominator += 2;
+    }
+  }
+
+
+  /*
+   * Parse the value of a new Decimal `x` from string `str`.
+   */
+  function parseDecimal(x, str) {
+    var e, i, len;
+
+    // Decimal point?
+    if ((e = str.indexOf('.')) > -1) str = str.replace('.', '');
+
+    // Exponential form?
+    if ((i = str.search(/e/i)) > 0) {
+
+      // Determine exponent.
+      if (e < 0) e = i;
+      e += +str.slice(i + 1);
+      str = str.substring(0, i);
+    } else if (e < 0) {
+
+      // Integer.
+      e = str.length;
+    }
+
+    // Determine leading zeros.
+    for (i = 0; str.charCodeAt(i) === 48;) ++i;
+
+    // Determine trailing zeros.
+    for (len = str.length; str.charCodeAt(len - 1) === 48;) --len;
+    str = str.slice(i, len);
+
+    if (str) {
+      len -= i;
+      e = e - i - 1;
+      x.e = mathfloor(e / LOG_BASE);
+      x.d = [];
+
+      // Transform base
+
+      // e is the base 10 exponent.
+      // i is where to slice str to get the first word of the digits array.
+      i = (e + 1) % LOG_BASE;
+      if (e < 0) i += LOG_BASE;
+
+      if (i < len) {
+        if (i) x.d.push(+str.slice(0, i));
+        for (len -= LOG_BASE; i < len;) x.d.push(+str.slice(i, i += LOG_BASE));
+        str = str.slice(i);
+        i = LOG_BASE - str.length;
+      } else {
+        i -= len;
+      }
+
+      for (; i--;) str += '0';
+      x.d.push(+str);
+
+      if (external && (x.e > MAX_E || x.e < -MAX_E)) throw Error(exponentOutOfRange + e);
+    } else {
+
+      // Zero.
+      x.s = 0;
+      x.e = 0;
+      x.d = [0];
+    }
+
+    return x;
+  }
+
+
+  /*
+   * Round `x` to `sd` significant digits, using rounding mode `rm` if present (truncate otherwise).
+   */
+   function round(x, sd, rm) {
+    var i, j, k, n, rd, doRound, w, xdi,
+      xd = x.d;
+
+    // rd: the rounding digit, i.e. the digit after the digit that may be rounded up.
+    // w: the word of xd which contains the rounding digit, a base 1e7 number.
+    // xdi: the index of w within xd.
+    // n: the number of digits of w.
+    // i: what would be the index of rd within w if all the numbers were 7 digits long (i.e. if
+    // they had leading zeros)
+    // j: if > 0, the actual index of rd within w (if < 0, rd is a leading zero).
+
+    // Get the length of the first word of the digits array xd.
+    for (n = 1, k = xd[0]; k >= 10; k /= 10) n++;
+    i = sd - n;
+
+    // Is the rounding digit in the first word of xd?
+    if (i < 0) {
+      i += LOG_BASE;
+      j = sd;
+      w = xd[xdi = 0];
+    } else {
+      xdi = Math.ceil((i + 1) / LOG_BASE);
+      k = xd.length;
+      if (xdi >= k) return x;
+      w = k = xd[xdi];
+
+      // Get the number of digits of w.
+      for (n = 1; k >= 10; k /= 10) n++;
+
+      // Get the index of rd within w.
+      i %= LOG_BASE;
+
+      // Get the index of rd within w, adjusted for leading zeros.
+      // The number of leading zeros of w is given by LOG_BASE - n.
+      j = i - LOG_BASE + n;
+    }
+
+    if (rm !== void 0) {
+      k = mathpow(10, n - j - 1);
+
+      // Get the rounding digit at index j of w.
+      rd = w / k % 10 | 0;
+
+      // Are there any non-zero digits after the rounding digit?
+      doRound = sd < 0 || xd[xdi + 1] !== void 0 || w % k;
+
+      // The expression `w % mathpow(10, n - j - 1)` returns all the digits of w to the right of the
+      // digit at (left-to-right) index j, e.g. if w is 908714 and j is 2, the expression will give
+      // 714.
+
+      doRound = rm < 4
+        ? (rd || doRound) && (rm == 0 || rm == (x.s < 0 ? 3 : 2))
+        : rd > 5 || rd == 5 && (rm == 4 || doRound || rm == 6 &&
+
+          // Check whether the digit to the left of the rounding digit is odd.
+          ((i > 0 ? j > 0 ? w / mathpow(10, n - j) : 0 : xd[xdi - 1]) % 10) & 1 ||
+            rm == (x.s < 0 ? 8 : 7));
+    }
+
+    if (sd < 1 || !xd[0]) {
+      if (doRound) {
+        k = getBase10Exponent(x);
+        xd.length = 1;
+
+        // Convert sd to decimal places.
+        sd = sd - k - 1;
+
+        // 1, 0.1, 0.01, 0.001, 0.0001 etc.
+        xd[0] = mathpow(10, (LOG_BASE - sd % LOG_BASE) % LOG_BASE);
+        x.e = mathfloor(-sd / LOG_BASE) || 0;
+      } else {
+        xd.length = 1;
+
+        // Zero.
+        xd[0] = x.e = x.s = 0;
+      }
+
+      return x;
+    }
+
+    // Remove excess digits.
+    if (i == 0) {
+      xd.length = xdi;
+      k = 1;
+      xdi--;
+    } else {
+      xd.length = xdi + 1;
+      k = mathpow(10, LOG_BASE - i);
+
+      // E.g. 56700 becomes 56000 if 7 is the rounding digit.
+      // j > 0 means i > number of leading zeros of w.
+      xd[xdi] = j > 0 ? (w / mathpow(10, n - j) % mathpow(10, j) | 0) * k : 0;
+    }
+
+    if (doRound) {
+      for (;;) {
+
+        // Is the digit to be rounded up in the first word of xd?
+        if (xdi == 0) {
+          if ((xd[0] += k) == BASE) {
+            xd[0] = 1;
+            ++x.e;
+          }
+
+          break;
+        } else {
+          xd[xdi] += k;
+          if (xd[xdi] != BASE) break;
+          xd[xdi--] = 0;
+          k = 1;
+        }
+      }
+    }
+
+    // Remove trailing zeros.
+    for (i = xd.length; xd[--i] === 0;) xd.pop();
+
+    if (external && (x.e > MAX_E || x.e < -MAX_E)) {
+      throw Error(exponentOutOfRange + getBase10Exponent(x));
+    }
+
+    return x;
+  }
+
+
+  function subtract(x, y) {
+    var d, e, i, j, k, len, xd, xe, xLTy, yd,
+      Ctor = x.constructor,
+      pr = Ctor.precision;
+
+    // Return y negated if x is zero.
+    // Return x if y is zero and x is non-zero.
+    if (!x.s || !y.s) {
+      if (y.s) y.s = -y.s;
+      else y = new Ctor(x);
+      return external ? round(y, pr) : y;
+    }
+
+    xd = x.d;
+    yd = y.d;
+
+    // x and y are non-zero numbers with the same sign.
+
+    e = y.e;
+    xe = x.e;
+    xd = xd.slice();
+    k = xe - e;
+
+    // If exponents differ...
+    if (k) {
+      xLTy = k < 0;
+
+      if (xLTy) {
+        d = xd;
+        k = -k;
+        len = yd.length;
+      } else {
+        d = yd;
+        e = xe;
+        len = xd.length;
+      }
+
+      // Numbers with massively different exponents would result in a very high number of zeros
+      // needing to be prepended, but this can be avoided while still ensuring correct rounding by
+      // limiting the number of zeros to `Math.ceil(pr / LOG_BASE) + 2`.
+      i = Math.max(Math.ceil(pr / LOG_BASE), len) + 2;
+
+      if (k > i) {
+        k = i;
+        d.length = 1;
+      }
+
+      // Prepend zeros to equalise exponents.
+      d.reverse();
+      for (i = k; i--;) d.push(0);
+      d.reverse();
+
+    // Base 1e7 exponents equal.
+    } else {
+
+      // Check digits to determine which is the bigger number.
+
+      i = xd.length;
+      len = yd.length;
+      xLTy = i < len;
+      if (xLTy) len = i;
+
+      for (i = 0; i < len; i++) {
+        if (xd[i] != yd[i]) {
+          xLTy = xd[i] < yd[i];
+          break;
+        }
+      }
+
+      k = 0;
+    }
+
+    if (xLTy) {
+      d = xd;
+      xd = yd;
+      yd = d;
+      y.s = -y.s;
+    }
+
+    len = xd.length;
+
+    // Append zeros to xd if shorter.
+    // Don't add zeros to yd if shorter as subtraction only needs to start at yd length.
+    for (i = yd.length - len; i > 0; --i) xd[len++] = 0;
+
+    // Subtract yd from xd.
+    for (i = yd.length; i > k;) {
+      if (xd[--i] < yd[i]) {
+        for (j = i; j && xd[--j] === 0;) xd[j] = BASE - 1;
+        --xd[j];
+        xd[i] += BASE;
+      }
+
+      xd[i] -= yd[i];
+    }
+
+    // Remove trailing zeros.
+    for (; xd[--len] === 0;) xd.pop();
+
+    // Remove leading zeros and adjust exponent accordingly.
+    for (; xd[0] === 0; xd.shift()) --e;
+
+    // Zero?
+    if (!xd[0]) return new Ctor(0);
+
+    y.d = xd;
+    y.e = e;
+
+    //return external && xd.length >= pr / LOG_BASE ? round(y, pr) : y;
+    return external ? round(y, pr) : y;
+  }
+
+
+  function toString(x, isExp, sd) {
+    var k,
+      e = getBase10Exponent(x),
+      str = digitsToString(x.d),
+      len = str.length;
+
+    if (isExp) {
+      if (sd && (k = sd - len) > 0) {
+        str = str.charAt(0) + '.' + str.slice(1) + getZeroString(k);
+      } else if (len > 1) {
+        str = str.charAt(0) + '.' + str.slice(1);
+      }
+
+      str = str + (e < 0 ? 'e' : 'e+') + e;
+    } else if (e < 0) {
+      str = '0.' + getZeroString(-e - 1) + str;
+      if (sd && (k = sd - len) > 0) str += getZeroString(k);
+    } else if (e >= len) {
+      str += getZeroString(e + 1 - len);
+      if (sd && (k = sd - e - 1) > 0) str = str + '.' + getZeroString(k);
+    } else {
+      if ((k = e + 1) < len) str = str.slice(0, k) + '.' + str.slice(k);
+      if (sd && (k = sd - len) > 0) {
+        if (e + 1 === len) str += '.';
+        str += getZeroString(k);
+      }
+    }
+
+    return x.s < 0 ? '-' + str : str;
+  }
+
+
+  // Does not strip trailing zeros.
+  function truncate(arr, len) {
+    if (arr.length > len) {
+      arr.length = len;
+      return true;
+    }
+  }
+
+
+  // Decimal methods
+
+
+  /*
+   *  clone
+   *  config/set
+   */
+
+
+  /*
+   * Create and return a Decimal constructor with the same configuration properties as this Decimal
+   * constructor.
+   *
+   */
+  function clone(obj) {
+    var i, p, ps;
+
+    /*
+     * The Decimal constructor and exported function.
+     * Return a new Decimal instance.
+     *
+     * value {number|string|Decimal} A numeric value.
+     *
+     */
+    function Decimal(value) {
+      var x = this;
+
+      // Decimal called without new.
+      if (!(x instanceof Decimal)) return new Decimal(value);
+
+      // Retain a reference to this Decimal constructor, and shadow Decimal.prototype.constructor
+      // which points to Object.
+      x.constructor = Decimal;
+
+      // Duplicate.
+      if (value instanceof Decimal) {
+        x.s = value.s;
+        x.e = value.e;
+        x.d = (value = value.d) ? value.slice() : value;
+        return;
+      }
+
+      if (typeof value === 'number') {
+
+        // Reject Infinity/NaN.
+        if (value * 0 !== 0) {
+          throw Error(invalidArgument + value);
+        }
+
+        if (value > 0) {
+          x.s = 1;
+        } else if (value < 0) {
+          value = -value;
+          x.s = -1;
+        } else {
+          x.s = 0;
+          x.e = 0;
+          x.d = [0];
+          return;
+        }
+
+        // Fast path for small integers.
+        if (value === ~~value && value < 1e7) {
+          x.e = 0;
+          x.d = [value];
+          return;
+        }
+
+        return parseDecimal(x, value.toString());
+      } else if (typeof value !== 'string') {
+        throw Error(invalidArgument + value);
+      }
+
+      // Minus sign?
+      if (value.charCodeAt(0) === 45) {
+        value = value.slice(1);
+        x.s = -1;
+      } else {
+        x.s = 1;
+      }
+
+      if (isDecimal.test(value)) parseDecimal(x, value);
+      else throw Error(invalidArgument + value);
+    }
+
+    Decimal.prototype = P;
+
+    Decimal.ROUND_UP = 0;
+    Decimal.ROUND_DOWN = 1;
+    Decimal.ROUND_CEIL = 2;
+    Decimal.ROUND_FLOOR = 3;
+    Decimal.ROUND_HALF_UP = 4;
+    Decimal.ROUND_HALF_DOWN = 5;
+    Decimal.ROUND_HALF_EVEN = 6;
+    Decimal.ROUND_HALF_CEIL = 7;
+    Decimal.ROUND_HALF_FLOOR = 8;
+
+    Decimal.clone = clone;
+    Decimal.config = Decimal.set = config;
+
+    if (obj === void 0) obj = {};
+    if (obj) {
+      ps = ['precision', 'rounding', 'toExpNeg', 'toExpPos', 'LN10'];
+      for (i = 0; i < ps.length;) if (!obj.hasOwnProperty(p = ps[i++])) obj[p] = this[p];
+    }
+
+    Decimal.config(obj);
+
+    return Decimal;
+  }
+
+
+  /*
+   * Configure global settings for a Decimal constructor.
+   *
+   * `obj` is an object with one or more of the following properties,
+   *
+   *   precision  {number}
+   *   rounding   {number}
+   *   toExpNeg   {number}
+   *   toExpPos   {number}
+   *
+   * E.g. Decimal.config({ precision: 20, rounding: 4 })
+   *
+   */
+  function config(obj) {
+    if (!obj || typeof obj !== 'object') {
+      throw Error(decimalError + 'Object expected');
+    }
+    var i, p, v,
+      ps = [
+        'precision', 1, MAX_DIGITS,
+        'rounding', 0, 8,
+        'toExpNeg', -1 / 0, 0,
+        'toExpPos', 0, 1 / 0
+      ];
+
+    for (i = 0; i < ps.length; i += 3) {
+      if ((v = obj[p = ps[i]]) !== void 0) {
+        if (mathfloor(v) === v && v >= ps[i + 1] && v <= ps[i + 2]) this[p] = v;
+        else throw Error(invalidArgument + p + ': ' + v);
+      }
+    }
+
+    if ((v = obj[p = 'LN10']) !== void 0) {
+        if (v == Math.LN10) this[p] = new this(v);
+        else throw Error(invalidArgument + p + ': ' + v);
+    }
+
+    return this;
+  }
+
+
+  // Create and configure initial Decimal constructor.
+  Decimal = clone(Decimal);
+
+  Decimal['default'] = Decimal.Decimal = Decimal;
+
+  // Internal constant.
+  ONE = new Decimal(1);
+
+
+  // Export.
+
+
+  // AMD.
+  if (typeof define == 'function' && define.amd) {
+    define(function () {
+      return Decimal;
+    });
+
+  // Node and other environments that support module.exports.
+  } else if (typeof module != 'undefined' && module.exports) {
+    module.exports = Decimal;
+
+    // Browser.
+  } else {
+    if (!globalScope) {
+      globalScope = typeof self != 'undefined' && self && self.self == self
+        ? self : Function('return this')();
+    }
+
+    globalScope.Decimal = Decimal;
+  }
+})(this);
