Exploring advanced mathematical calculations in QtQuick Qml with JavaScript for handling large numbers

Question

Exploring advanced mathematical calculations in QtQuick Qml with JavaScript for handling large numbers

I need to calculate the orbit of the Sun around the Galaxy. The mathematical formula I am using is ((241828072282107.5071453596951 * 666) * 2) * 3.14159265359. In QML JavaScript, I received the answer 1011954093357316100, but the correct answer is 1011954093357316200, off by 100 units.

galaxyRadius="241828072282107.5071453596951";

currentTrackNumber=666; // Track Number like on a Record

pIe="3.14159265359"; // not the same as Math.PI

I had to keep the numbers as strings because converting them to floats would lose precision. Converting an old bash script to JavaScript, I realized it worked fine with bc but not with Math.

I tried the following:

orbitDist = ((( Number.parseFloat(galaxyRadius).toPrecision(20) * currentTrackNumber) * 2) * Number.parseFloat(pIe).toPrecision(12) );

The results are the same as:

orbitDist = ((( galaxyRadius * currentTrackNumber) * 2) * pIe );

Compared to the bash result:

echo "$(bc <<< "scale=13;((241828072282107.5071453596951 * 666) * 2) * 3.14159265359")"

Bash is accurate while JavaScript is inaccurate by almost 100 units. This discrepancy is concerning, especially since I have many numbers that are slightly off. A 100-unit difference is not acceptable.

I prefer to work with integers rather than exponents. The values are stored in a database as strings, so I just need the math to be precise.

This is a QtQuick, QML, Felgo App using Qml and JavaScript, designed to run on various platforms. My next step is to consider C++ or a math library that suits this project. A JavaScript or QML wrapper library for C++ would be ideal. I have researched JavaScript libraries for the web, but they require extensive modifications for Qml. I am looking for a solution that works seamlessly.

javascript bash qt math qml

Answer 1

Answer №1

In the current state, JavaScript only supports bignum for integers (BigInt). Therefore, I convert the numbers to BigInt before performing calculations and keep track of the decimal part to convert back to float.

const galaxyRadius="241828072282107.5071453596951";

const currentTrackNumber=666; // Track Number like on a Record

const pIe="3.14159265359"; // not the same as Math.PI

const orbitDist = ((( galaxyRadius * currentTrackNumber) * 2) * pIe );
console.log(orbitDist)

//// My approad

//Put all number into an array
var arrToMul = [galaxyRadius,currentTrackNumber, 2, pIe]

// Function multiple all item in array with BigInt format
function mulBigInt(arr) {
  return arr.reduce(function (acc, e) {
    return BigInt(e) * acc;
  }, BigInt(1));
}; 

// Function get length of decimal part
function decLength(str) {
  var dec = str.toString().split('.')[1];
  return dec ? dec.length : 0;
}; 

// Function remove point in string to convert float to int
function rmPoint(strNum) {
  return strNum.toString().replace('.', "");
}; 

// Main function
function cal(arr) {
  // Get total decimal part length of all number
  var pointSize = arr.reduce(function (acc, e) {
    return acc + decLength(e);
  }, 0); 
  
  // convert the all item to int (type string)
  var newArr = arr.map(function (e) {
    return rmPoint(e);
  }); 
  // Add point to reconvert BigInt to float(string actually)
  var tmp = mulBigInt(newArr).toString().split('');
  tmp.splice(tmp.length - pointSize, 0, '.'); 
  
  // Return float result with string format
  return tmp.join('');
};
const rs = cal(arrToMul)
console.log(rs, 'converted to BigInt:')

Answer 2

In the current state, JavaScript only supports bignum for integers (BigInt). Therefore, I convert the numbers to BigInt before performing calculations and keep track of the decimal part to convert back to float.

const galaxyRadius="241828072282107.5071453596951";

const currentTrackNumber=666; // Track Number like on a Record

const pIe="3.14159265359"; // not the same as Math.PI

const orbitDist = ((( galaxyRadius * currentTrackNumber) * 2) * pIe );
console.log(orbitDist)

//// My approad

//Put all number into an array
var arrToMul = [galaxyRadius,currentTrackNumber, 2, pIe]

// Function multiple all item in array with BigInt format
function mulBigInt(arr) {
  return arr.reduce(function (acc, e) {
    return BigInt(e) * acc;
  }, BigInt(1));
}; 

// Function get length of decimal part
function decLength(str) {
  var dec = str.toString().split('.')[1];
  return dec ? dec.length : 0;
}; 

// Function remove point in string to convert float to int
function rmPoint(strNum) {
  return strNum.toString().replace('.', "");
}; 

// Main function
function cal(arr) {
  // Get total decimal part length of all number
  var pointSize = arr.reduce(function (acc, e) {
    return acc + decLength(e);
  }, 0); 
  
  // convert the all item to int (type string)
  var newArr = arr.map(function (e) {
    return rmPoint(e);
  }); 
  // Add point to reconvert BigInt to float(string actually)
  var tmp = mulBigInt(newArr).toString().split('');
  tmp.splice(tmp.length - pointSize, 0, '.'); 
  
  // Return float result with string format
  return tmp.join('');
};
const rs = cal(arrToMul)
console.log(rs, 'converted to BigInt:')

Exploring advanced mathematical calculations in QtQuick Qml with JavaScript for handling large numbers

Answer №1

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