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    Ds\Vector::reduce

    (PECL ds >= 1.0.0)

    Ds\Vector::reduce — Reduces the vector to a single value using a callback function

    説明

    public Ds\Vector::reduce(callable $callback, mixed $initial = ?): mixed

    Reduces the vector to a single value using a callback function.

    パラメータ

    callback
    callback(mixed $carry, mixed $value): mixed
    carry

    The return value of the previous callback, or initial if it's the first iteration.

    value

    The value of the current iteration.

    initial

    The initial value of the carry value. Can be null.

    戻り値

    The return value of the final callback.

    例

    例1 Ds\Vector::reduce() with initial value example

    <?php
    $vector     = new \Ds\Vector([1, 2, 3]);

    $callback = function($carry, $value) {
    return     $carry * $value;
    };

    var_dump($vector->reduce($callback, 5));

    // Iterations:
    //
    // $carry = $initial = 5
    //
    // $carry = $carry * 1 = 5
    // $carry = $carry * 2 = 10
    // $carry = $carry * 3 = 30
    ?>

    上の例の出力は、 たとえば以下のようになります。

    int(30)

    例2 Ds\Vector::reduce() without an initial value example

    <?php
    $vector     = new \Ds\Vector([1, 2, 3]);

    var_dump($vector->reduce(function($carry, $value) {
    return     $carry + $value + 5;
    }));

    // Iterations:
    //
    // $carry = $initial = null
    //
    // $carry = $carry + 1 + 5 = 6
    // $carry = $carry + 2 + 5 = 13
    // $carry = $carry + 3 + 5 = 21
    ?>

    上の例の出力は、 たとえば以下のようになります。

    int(21)
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