Simple rounding test failed

[palansher]

Hello!

I am trying to check the corrections of rounding. This simple test must be passed:

1/7/13713 = 1

But result discourages:

$brickRoundings=[
    RoundingMode::UP,
    RoundingMode::DOWN,
    RoundingMode::CEILING,
    RoundingMode::FLOOR,
    RoundingMode::HALF_UP,
    RoundingMode::HALF_DOWN,
    RoundingMode::HALF_CEILING,
    RoundingMode::HALF_FLOOR,
    RoundingMode::HALF_EVEN,
];
$money = Brick::of(1, 'EUR');
foreach ($brickRoundings as $brickRounding) {
    $brickResult=$money->dividedBy(7, $brickRounding)->dividedBy(13, $brickRounding)
        ->multipliedBy(7, $brickRounding)->multipliedBy(13, $brickRounding);
    echo 'brick: ' . $brickResult->formatTo('en_US').PHP_EOL;
}

brick: €1.82
brick: €0.91
brick: €1.82
brick: €0.91
brick: €0.91
brick: €0.91
brick: €0.91
brick: €0.91
brick: €0.91

the result is not 1 while even Windows 10 calculator app provides the correct answer =1. Excel, for sure also .. also PHP:

<?php
echo 1/7/13*7*13;
// =1

Would you please explain: why I cannot get the correct answer = 1?

thank you!

[palansher]

It seems I found right way using toRational():

$brickRoundings=[
    RoundingMode::UP,
    RoundingMode::DOWN,
    RoundingMode::CEILING,
    RoundingMode::FLOOR,
    RoundingMode::HALF_UP,
    RoundingMode::HALF_DOWN,
    RoundingMode::HALF_CEILING,
    RoundingMode::HALF_FLOOR,
    RoundingMode::HALF_EVEN,
];

$brickMoney = Brick::of(1, 'EUR');
foreach ($brickRoundings as $brickRounding) {
    $brickMoney->toRational()
    ->dividedBy(7, $brickRounding)
    ->dividedBy(13, $brickRounding)
    ->multipliedBy(7, $brickRounding)
    ->multipliedBy(13, $brickRounding)    
    ->to($brickMoney->getContext(), RoundingMode::UNNECESSARY)->formatTo('en_US');
    echo 'brick: ' . $brickMoney. PHP_EOL;
}

now the result is correct and =1 with and without rounding :

brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00
brick: EUR 1.00

So, you can close the ticket if you have no comments. Thanks for the good tool!

[BenMorel]

Hi, glad you figured it out! Yes of course, if you apply roundings along the way, you'll end up with the incorrect amount at the end. As you've discovered, RationalMoney is the way to go for exact calculations! :+1: