decimal128/examples/midprice.js

Partial implementation of IEEE 754 Decimal128 decimal floating-point numbers

import { Decimal128 } from "../src/Decimal128.mjs";
function getRandomInt(max) {
    return Math.floor(Math.random() * max);
}
function getRandomDigits(n) {
    let digits = [];
    for (let i = 0; i < n; i++) {
        digits.push(getRandomInt(10));
    }
    return digits;
}
function getRandomDigitsAsString(n) {
    let digits = getRandomDigits(n + 4);
    return digits.slice(0, n).join("") + "." + digits.slice(n).join("");
}
const two = new Decimal128(2);
function compareNumbers(digits1, digits2) {
    let d1 = new Decimal128(digits1);
    let d2 = new Decimal128(digits2);
    let decimalResult = d1.add(d2).divide(two);
    let numberResult = (Number(digits1) + Number(digits2)) / 2;
    let numberResultString = numberResult.toFixed(4);
    let decimalResultString = decimalResult.toFixed({ digits: 4 });
    return [numberResultString, decimalResultString];
}
function keepTrying() {
    let digits1 = getRandomDigitsAsString(3);
    let digits2 = getRandomDigitsAsString(3);
    let [result1, result2] = compareNumbers(digits1, digits2);
    if (result1 !== result2) {
        let diff = new Decimal128(result1)
            .subtract(new Decimal128(result2))
            .abs();
        console.log(`(${digits1} + ${digits2})/2 = ${result1} but it should be ${result2} (difference: ${diff.toString()})`);
    }
    return result1 !== result2;
}
let numAttempts = 1000;
let numFailures = 0;
for (let i = 0; i < numAttempts; i++) {
    let failed = keepTrying();
    if (failed) {
        numFailures++;
    }
}
console.log(`Failed ${numFailures} out of ${numAttempts} attempts`);