function Calculator::divRound

Performs a rounded division.

Rounding is performed when the remainder of the division is not zero.

@psalm-suppress ImpureFunctionCall

Parameters

string $a The dividend.:

string $b The divisor, must not be zero.:

RoundingMode $roundingMode The rounding mode.:

Throws

\InvalidArgumentException If the rounding mode is invalid.

RoundingNecessaryException If RoundingMode::UNNECESSARY is provided but rounding is necessary.

File

vendor/brick/math/src/Internal/Calculator.php, line 442

Class

Calculator

Performs basic operations on arbitrary size integers.

Namespace

Brick\Math\Internal

Code

public final function divRound(string $a, string $b, RoundingMode $roundingMode) : string {
    [
        $quotient,
        $remainder,
    ] = $this->divQR($a, $b);
    $hasDiscardedFraction = $remainder !== '0';
    $isPositiveOrZero = ($a[0] === '-') === ($b[0] === '-');
    $discardedFractionSign = function () use ($remainder, $b) : int {
        $r = $this->abs($this->mul($remainder, '2'));
        $b = $this->abs($b);
        return $this->cmp($r, $b);
    };
    $increment = false;
    switch ($roundingMode) {
        case RoundingMode::UNNECESSARY:
            if ($hasDiscardedFraction) {
                throw RoundingNecessaryException::roundingNecessary();
            }
            break;
        case RoundingMode::UP:
            $increment = $hasDiscardedFraction;
            break;
        case RoundingMode::DOWN:
            break;
        case RoundingMode::CEILING:
            $increment = $hasDiscardedFraction && $isPositiveOrZero;
            break;
        case RoundingMode::FLOOR:
            $increment = $hasDiscardedFraction && !$isPositiveOrZero;
            break;
        case RoundingMode::HALF_UP:
            $increment = $discardedFractionSign() >= 0;
            break;
        case RoundingMode::HALF_DOWN:
            $increment = $discardedFractionSign() > 0;
            break;
        case RoundingMode::HALF_CEILING:
            $increment = $isPositiveOrZero ? $discardedFractionSign() >= 0 : $discardedFractionSign() > 0;
            break;
        case RoundingMode::HALF_FLOOR:
            $increment = $isPositiveOrZero ? $discardedFractionSign() > 0 : $discardedFractionSign() >= 0;
            break;
        case RoundingMode::HALF_EVEN:
            $lastDigit = (int) $quotient[-1];
            $lastDigitIsEven = $lastDigit % 2 === 0;
            $increment = $lastDigitIsEven ? $discardedFractionSign() > 0 : $discardedFractionSign() >= 0;
            break;
        default:
            throw new \InvalidArgumentException('Invalid rounding mode.');
    }
    if ($increment) {
        return $this->add($quotient, $isPositiveOrZero ? '1' : '-1');
    }
    return $quotient;
}