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@ 2020-08-01T20:22:58Z

<?php


function is_even(int $n): bool {
        if ($n < 0) {
            $n = abs($n);
        }
        
        if ($n === 0) {
            return true;
        }
        
        if ($n === 1) {
            return false;
        }
        
        return is_even($n - 1);
}

for($i = -5; $i <= 12; $i++) {
    printf('is %d even? %s.%s', $i, is_even($i) ? 'yes': 'no', "\n");
}

Output
Performance
VLD
References
Branches

abs: documentation ( source)
printf: documentation ( source)

preferences:dark modelive preview

46.67 ms | 402 KiB | 5 Q