Lazy calculation implementation of array intersection and union in PHP

PHP Lazy calculation of array intersections and unions In PHP, you can use generators to implement lazy calculations of array intersections and unions to delay the calculation of the results until needed: Intersection: Use the array_intersect_lazy() generator, only if the array Iterate and output only when the elements are equal. Union: Using the array_union_lazy() generator, iterate over two arrays and output them to the result, filtering out duplicate elements.

PHP Lazy calculation implementation of array intersection and union

In PHP, it is common to process array intersection and union operate. Usually, we will use the array_intersect() and array_merge() functions to implement these operations. However, this causes the result to be calculated immediately, which can sometimes cause performance issues, especially with large arrays.

Lazy calculation solves this problem by allowing us to delay calculation until the result is actually needed. Using generators we can easily implement lazily computed array intersections and unions.

Implementation

##Intersection

function array_intersect_lazy($array1, $array2) {
    foreach ($array1 as $key => $value) {
        if (isset($array2[$key]) && $value === $array2[$key]) {
            yield $value;
        }
    }
}

Union

function array_union_lazy($array1, $array2) {
    foreach ($array1 as $key => $value) {
        yield $value;
    }

    foreach ($array2 as $key => $value) {
        if (!isset($array1[$key])) {
            yield $value;
        }
    }
}

Practical Case

$array1 = ['foo', 'bar', 'baz'];
$array2 = ['bar', 'qux', 'quux'];

foreach (array_intersect_lazy($array1, $array2) as $value) {
    echo "$value\n";
}

// 输出：
// bar

foreach (array_union_lazy($array1, $array2) as $value) {
    echo "$value\n";
}

// 输出：
// foo
// bar
// baz
// qux
// quux

These generators allow us to iterate and print the intersection or union directly without waiting for the entire result calculation to complete. This can significantly improve performance on large arrays.

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