Skip to content

Latest commit

 

History

History
187 lines (164 loc) · 4.13 KB

README.md

File metadata and controls

187 lines (164 loc) · 4.13 KB
Raw

babel-plugin-transform-bigint

Update: Now it can convert a code using BigInt into a code using JSBI (https://github.com/GoogleChromeLabs/jsbi). It will try to detect when an operator is used for bigints, not numbers. This will not work in many cases, so please use JSBI directly only if you know, that the code works only with bigints.

An example from https://github.com/GoogleChromeLabs/babel-plugin-transform-jsbi-to-bigint:

Input using native BigInts:

const a = BigInt(Number.MAX_SAFE_INTEGER);
const b = 2n;

a + b;
a - b;
a * b;
a / b;
a % b;
a ** b;
a << b;
a >> b;
a & b;
a | b;
a ^ b;

-a;
~a;

a === b;
a < b;
a <= b;
a > b;
a >= b;

a.toString();
Number(a);

Compiled output using JSBI:

const a = JSBI.BigInt(Number.MAX_SAFE_INTEGER);
const b = JSBI.BigInt(2);
JSBI.add(a, b);
JSBI.subtract(a, b);
JSBI.multiply(a, b);
JSBI.divide(a, b);
JSBI.remainder(a, b);
JSBI.exponentiate(a, b);
JSBI.leftShift(a, b);
JSBI.signedRightShift(a, b);
JSBI.bitwiseAnd(a, b);
JSBI.bitwiseOr(a, b);
JSBI.bitwiseXor(a, b);
JSBI.unaryMinus(a);
JSBI.bitwiseNot(a);
JSBI.equal(a, b);
JSBI.lessThan(a, b);
JSBI.lessThanOrEqual(a, b);
JSBI.greaterThan(a, b);
JSBI.greaterThanOrEqual(a, b);
a.toString();
JSBI.toNumber(a);

Playground:

  1. Open https://babeljs.io/en/repl
  2. Turn off all presets.
  3. "Add plugin" @babel/babel-plugin-syntax-bigint
  4. "Add plugin" babel-plugin-transform-bigint

¡ It is buggy !

Example:

  1. Create a folder "example".
  2. Create a file test.js:
// floor(log2(n)), n >= 1
function ilog2(n) {
  let i = 0n;
  while (n >= 2n**(2n**i)) {
    i += 1n;
  }
  let e = 0n;
  let t = 1n;
  while (i >= 0n) {
    let b = 2n**i;
    if (n >= t * 2n**b) {
      t *= 2n**b;
      e += b;
    }
    i -= 1n;
  }
  return e;
}

// floor(sqrt(S)), S >= 0, https://en.wikipedia.org/wiki/Methods_of_computing_square_roots#Babylonian_method
function sqrt(S) {
  let e = ilog2(S);
  if (e < 2n) {
    return 1n;
  }
  let f = e / 4n + 1n;
  let x = (sqrt(S / 2n**(f * 2n)) + 1n) * 2n**f;
  let xprev = x + 1n;
  while (xprev > x) {
    xprev = x;
    x = (x + S / x) / 2n;
  }
  return xprev;
}

function squareRoot(value, decimalDigits) {
  return (sqrt(BigInt(value) * 10n**(BigInt(decimalDigits) * 2n + 2n)) + 5n).toString();
}
  1. Use babel:
npm init
npm install --save https://github.com/Yaffle/babel-plugin-transform-bigint
npm install --save-dev @babel/core @babel/cli
npm install jsbi --save
npm install --global http-server
npx babel --plugins=babel-plugin-transform-bigint test.js > test-transformed.js
http-server -p 8081
  1. Comment out the next line in test-transformed.js:
import JSBI from "./jsbi.mjs";
  1. Create a file test.html.
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8" />
  <script src="./node_modules/jsbi/dist/jsbi-umd.js"></script>
  <script src="test-transformed.js"></script>
  <script>
    document.addEventListener("DOMContentLoaded", function (event) {
      const form = document.querySelector("form");
      form.oninput = function () {
        const value = form.value.value;
        const digits = Number(form.digits.value);
        const s = squareRoot(value, digits);
        // IE 11 does not support <output> element, so `form.output.value = "value";` is not working.
        form.querySelector("output").textContent = '√' + value +  ' ≈ ' + s.slice(0, 0 - digits - 1) + '.' + s.slice(0 - digits - 1, -1) + '…';
      };
      form.oninput();
    }, false);
  </script>
  <style>
    output {
      overflow-wrap: break-word;
    }
  </style>
</head>
<body>
  <form>
    <div>
      <label for="value">Value:</label>
      <input id="value" name="value" type="number" min="2" step="1" value="2" />
    </div>
    <div>
      <label for="digits">Number of decimal digits:</label>
      <input id="digits" name="digits" type="number" min="1" step="1" value="100" />
    </div>
    <div>
      <output id="output" name="output" for="value digits" tabindex="0"></output>
    </div>
  </form>
</body>
</html>
  1. Open http://127.0.0.1:8081/test.html in a web browser.