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https://github.com/yaffle/babel-plugin-transform-bigint

A plugin for babel to transform `x * y` into something like `JSBI.multiply(x, y)` to support bigints.
https://github.com/yaffle/babel-plugin-transform-bigint

Last synced: 8 days ago
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A plugin for babel to transform `x * y` into something like `JSBI.multiply(x, y)` to support bigints.

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README 

        
# 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 `BigInt`s:



```javascript

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:

```javascript

// 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();

}



```



3. Use babel:

```sh

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

```



4. Comment out the next line in test-transformed.js:

```javascript

import JSBI from "./jsbi.mjs";

```



5. Create a file `test.html`.

```html



  

  

  

  

    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);

  

  

    output {

      overflow-wrap: break-word;

    }

  



  

    


      Value:

      

    


    


      Number of decimal digits:

      

    


    


      

    


  



```



6. Open `http://127.0.0.1:8081/test.html` in a web browser.