@yaffle/bigdecimal - npm Package Compare versions

Comparing version 1.0.23 to 1.0.24

BigDecimal.js

@@ -32,2 +32,4 @@ /*jslint bigint: true, vars: true, indent: 2*/
 // BigDecimal.atan(a, rounding)
+// BigDecimal.sqrt(a, rounding)
+// BigDecimal.cbrt(a, rounding)
 // "simple" Math functions:
@@ -565,3 +567,3 @@ // BigDecimal.abs(a)
   const ten = BigDecimal.BigDecimal(10);
-  const minimumSignificantDigits = Math.pow(2, Math.ceil(Math.log2(bitLength(bigIntAbs(BigInt(value.exponent)) + 1n) / Math.log2(BASE))))
+  const minimumSignificantDigits = Math.pow(2, Math.ceil(Math.log2(bitLength(bigIntAbs(BigInt(value.exponent)) + 1n) / Math.log2(BASE))));
   let rounding = {maximumSignificantDigits: Math.max(minimumSignificantDigits, 8), roundingMode: "half-even"};
@@ -656,5 +658,5 @@ let result = undefined;
     if (!BigDecimal.equal(BigDecimal.round(a, {maximumSignificantDigits: middle, roundingMode: "half-even"}), a)) {
+      from = middle;
+    } else {
       to = middle;
-    } else {
-      from = middle;
     }
@@ -806,4 +808,6 @@ }
       const k = BigDecimal.round(BigDecimal.divide(x, logBASE, {maximumSignificantDigits: Math.max(Number(getCountOfDigits(x)), 1), roundingMode: "half-even"}), {maximumFractionDigits: 0, roundingMode: "half-even"});
-      const r = BigDecimal.subtract(x, BigDecimal.multiply(k, logBASE));
-      return BigDecimal.multiply(exponentiate(BASE, BigDecimal.toBigInt(k)), BigDecimal.exp(r, internalRounding));
+      if (!BigDecimal.equal(k, BigDecimal.BigDecimal(0))) {
+        const r = BigDecimal.subtract(x, BigDecimal.multiply(k, logBASE));
+        return BigDecimal.multiply(exponentiate(BASE, BigDecimal.toBigInt(k)), BigDecimal.exp(r, internalRounding));
+      }
     }
@@ -943,2 +947,43 @@ }
 
+function nthRoot(x, n, rounding) {
+  const exponentiateX = function (x, n) {
+    return n === 1 ? x : (n % 2 === 0 ? exponentiateX(BigDecimal.multiply(x, x), n / 2) : BigDecimal.multiply(x, exponentiate(x, n - 1)));
+  };
+  if (BigDecimal.lessThan(x, BigDecimal.BigDecimal(0))) {
+    if (n % 2 === 0) {
+      throw new RangeError();
+    }
+  }
+  if (BigDecimal.equal(x, BigDecimal.BigDecimal(0))) {
+    return x;
+  }
+  // https://en.wikipedia.org/wiki/Nth_root#Using_Newton's_method
+  const e = getCountOfDigits(x) / BigInt(n);
+  const t = exponentiate(BASE, e);
+  const y = BigDecimal.multiply(x, exponentiate(BASE, -(BigInt(n) * e)));
+  const k = Math.floor(Math.log2(Number.MAX_SAFE_INTEGER + 1) / Math.log2(BASE)) - 1;
+  const xn = BigDecimal.toNumber(BigDecimal.round(BigDecimal.multiply(y, exponentiate(BASE, k)), {maximumFractionDigits: 0, roundingMode: 'half-even'})) / BASE**k;
+  const r = n === 2 ? Math.sqrt(xn) : (n === 3 ? Math.cbrt(xn) : Math.exp(Math.log(xn) / n));
+  const resultSignificantDigits = 8 * (rounding.maximumSignificantDigits || (rounding.maximumFractionDigits + Math.ceil(significandDigits(x) / n)) || 1);
+  let result = BigDecimal.multiply(BigDecimal.BigDecimal(Math.sign(r) * Math.floor(Math.abs(r) * BASE**k + 0.5)), exponentiate(BASE, -k));
+  const iteration = function (result, rounding) {
+    const resultInNm1 = exponentiateX(result, n - 1);
+    return BigDecimal.divide(BigDecimal.add(y, BigDecimal.multiply(BigDecimal.BigDecimal(n - 1), BigDecimal.multiply(result, resultInNm1))), BigDecimal.multiply(BigDecimal.BigDecimal(n), resultInNm1), rounding);
+  };
+  for (let i = Math.max(k - (n - 1), 1); i < resultSignificantDigits; i *= 2) {
+    const internalRounding = {maximumSignificantDigits: i, roundingMode: "half-even"};
+    result = iteration(result, internalRounding);
+  }
+  result = iteration(result, rounding);
+  return BigDecimal.multiply(result, t);
+}
+
+BigDecimal.sqrt = function (x, rounding) {
+  return nthRoot(x, 2, rounding);
+};
+
+BigDecimal.cbrt = function (x, rounding) {
+  return nthRoot(x, 3, rounding);
+};
+
   return BigDecimal;
@@ -945,0 +990,0 @@ };

package.json

 {
   "name": "@yaffle/bigdecimal",
-  "version": "1.0.23",
+  "version": "1.0.24",
   "description": "Arbitrary precision decimal arithmetic library. Polyfill for decimal proposal. Implemented on the top of BigInt.",
@@ -5,0 +5,0 @@ "main": "BigDecimal.js",

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increased by4.6%

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