comparing_floats.js

function round(value, precision) {
  return Number(Math.round(value + "e" + precision) + "e-" + precision)
}


function strictCompare(left, right) {
  console.log(`strictCompare(${left}, ${right})`);
  return left === right;
}

function badRelaxedCompare(left, right) {
  left = round(left, 9);
  right = round(right, 9);

  console.log(`badRelaxedCompare(${left}, ${right})`);
  return left === right;
}

function goodRelaxedCompare(left, right) {
  left = left.toPrecision(16);
  right = right.toPrecision(16);
  console.log(`goodRelaxedCompare(${left}, ${right})`);

  return left === right;
}




//var a = 0.3 - 0.1;
//var b = 0.2;

//var a = 100.3 + 100.1;
//var b = 200.4;

var a = 1000000000.2 + 1000000000.1;
var b = 2000000000.3;


console.log(`a: ${a}, b: ${b}`);
console.log(strictCompare(a, b));
console.log(badRelaxedCompare(a, b));
console.log(goodRelaxedCompare(a, b));