BcMath\Number
PHP マニュアル

BcMath\Number::round

任意精度数値を丸める

説明

public BcMath\Number BcMath\Number::round(int $precision = 0, RoundingMode $mode = RoundingMode::HalfAwayFromZero)

$this を、指定した precision(小数点以下の桁数)に丸めた値を返します。 precision を負またはゼロ(デフォルト) とすることも可能です。

パラメータ

precision

オプションで指定する、丸める桁数。

precision が正の値の場合、 num は 小数点以下、有効桁数 precision 桁に丸められます。

precision が負の場合、 num の 丸め処理は小数点より前の precision 桁に対して行われます。 つまり、一番近い pow(10, -$precision) の倍数に丸められます。 たとえば、precision が -1 の場合、 num は 一番近い10の倍数に、 precision が -2 の場合は 一番近い100の倍数に丸められる、という具合です。

mode
指定する丸めモード。詳しくは RoundingMode を参照してください。

戻り値

結果を新しい BcMath\Number オブジェクトとして返します。

エラー / 例外

このメソッドは、無効な mode が指定された場合に ValueError をスローします。

例

例1 BcMath\Number::round の例

<?php
var_dump(
    new BcMath\Number('3.4')->round(),
    new BcMath\Number('3.5')->round(),
    new BcMath\Number('3.6')->round(),
    new BcMath\Number('3.6')->round(0),
    new BcMath\Number('5.045')->round(2),
    new BcMath\Number('5.055')->round(2),
    new BcMath\Number('345')->round(-2),
    new BcMath\Number('345')->round(-3),
    new BcMath\Number('678')->round(-2),
    new BcMath\Number('678')->round(-3),
);
?>

上の例の出力は以下となります。

object(BcMath\Number)#2 (2) {
  ["value"]=>
  string(1) "3"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(1) "4"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(1) "4"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(1) "4"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#6 (2) {
  ["value"]=>
  string(4) "5.05"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(4) "5.06"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#8 (2) {
  ["value"]=>
  string(3) "300"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(1) "0"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#10 (2) {
  ["value"]=>
  string(3) "700"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(4) "1000"
  ["scale"]=>
  int(0)
}

例2 BcMath\Number::round で異なる precision を指定した例 

<?php
$number = new BcMath\Number('123.45');

var_dump(
    $number->round(3),
    $number->round(2),
    $number->round(1),
    $number->round(0),
    $number->round(-1),
    $number->round(-2),
    $number->round(-3),
);
?>

上の例の出力は以下となります。

object(BcMath\Number)#2 (2) {
  ["value"]=>
  string(6) "123.45"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(6) "123.45"
  ["scale"]=>
  int(2)
}
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(5) "123.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(3) "123"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#6 (2) {
  ["value"]=>
  string(3) "120"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(3) "100"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#8 (2) {
  ["value"]=>
  string(1) "0"
  ["scale"]=>
  int(0)
}

例3 BcMath\Number::round で異なる mode を指定した例 

<?php
echo 'Rounding modes with 9.5' . PHP_EOL;
$number = new BcMath\Number('9.5');
var_dump(
    $number->round(0, RoundingMode::HalfAwayFromZero),
    $number->round(0, RoundingMode::HalfTowardsZero),
    $number->round(0, RoundingMode::HalfEven),
    $number->round(0, RoundingMode::HalfOdd),
    $number->round(0, RoundingMode::TowardsZero),
    $number->round(0, RoundingMode::AwayFromZero),
    $number->round(0, RoundingMode::NegativeInfinity),
    $number->round(0, RoundingMode::PositiveInfinity),
);

echo PHP_EOL;
echo 'Rounding modes with 8.5' . PHP_EOL;
$number = new BcMath\Number('8.5');
var_dump(
    $number->round(0, RoundingMode::HalfAwayFromZero),
    $number->round(0, RoundingMode::HalfTowardsZero),
    $number->round(0, RoundingMode::HalfEven),
    $number->round(0, RoundingMode::HalfOdd),
    $number->round(0, RoundingMode::TowardsZero),
    $number->round(0, RoundingMode::AwayFromZero),
    $number->round(0, RoundingMode::NegativeInfinity),
    $number->round(0, RoundingMode::PositiveInfinity),
);
?>

上の例の出力は以下となります。

Rounding modes with 9.5
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#13 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#15 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#17 (2) {
  ["value"]=>
  string(2) "10"
  ["scale"]=>
  int(0)
}

Rounding modes with 8.5
object(BcMath\Number)#1 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#15 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#13 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(1) "8"
  ["scale"]=>
  int(0)
}
object(BcMath\Number)#3 (2) {
  ["value"]=>
  string(1) "9"
  ["scale"]=>
  int(0)
}

例4 BcMath\Number::round で precision を指定し、 異なる mode を指定した例 

<?php
$positive = new BcMath\Number('1.55');
$negative = new BcMath\Number('-1.55');

echo 'Using RoundingMode::HalfAwayFromZero with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::HalfAwayFromZero),
    $negative->round(1, RoundingMode::HalfAwayFromZero),
);

echo PHP_EOL;
echo 'Using RoundingMode::HalfTowardsZero with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::HalfTowardsZero),
    $negative->round(1, RoundingMode::HalfTowardsZero),
);

echo PHP_EOL;
echo 'Using RoundingMode::HalfEven with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::HalfEven),
    $negative->round(1, RoundingMode::HalfEven),
);

echo PHP_EOL;
echo 'Using RoundingMode::HalfOdd with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::HalfOdd),
    $negative->round(1, RoundingMode::HalfOdd),
);

echo PHP_EOL;
echo 'Using RoundingMode::TowardsZero with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::TowardsZero),
    $negative->round(1, RoundingMode::TowardsZero),
);

echo PHP_EOL;
echo 'Using RoundingMode::AwayFromZero with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::AwayFromZero),
    $negative->round(1, RoundingMode::AwayFromZero),
);

echo PHP_EOL;
echo 'Using RoundingMode::NegativeInfinity with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::NegativeInfinity),
    $negative->round(1, RoundingMode::NegativeInfinity),
);

echo PHP_EOL;
echo 'Using RoundingMode::PositiveInfinity with 1 decimal digit precision' . PHP_EOL;
var_dump(
    $positive->round(1, RoundingMode::PositiveInfinity),
    $negative->round(1, RoundingMode::PositiveInfinity),
);
?>

上の例の出力は以下となります。

Using RoundingMode::HalfAwayFromZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#5 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::HalfTowardsZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#6 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

Using RoundingMode::HalfEven with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#7 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::HalfOdd with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#8 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

Using RoundingMode::TowardsZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#9 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

Using RoundingMode::AwayFromZero with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#10 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::NegativeInfinity with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.5"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#11 (2) {
  ["value"]=>
  string(4) "-1.6"
  ["scale"]=>
  int(1)
}

Using RoundingMode::PositiveInfinity with 1 decimal digit precision
object(BcMath\Number)#4 (2) {
  ["value"]=>
  string(3) "1.6"
  ["scale"]=>
  int(1)
}
object(BcMath\Number)#12 (2) {
  ["value"]=>
  string(4) "-1.5"
  ["scale"]=>
  int(1)
}

参考

  • bcround
  • BcMath\Number::ceil
  • BcMath\Number::floor