38 lines
1.2 KiB
PHP
38 lines
1.2 KiB
PHP
<?php
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/*
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* By adding type hints and enabling strict type checking, code can become
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* easier to read, self-documenting and reduce the number of potential bugs.
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* By default, type declarations are non-strict, which means they will attempt
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* to change the original type to match the type specified by the
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* type-declaration.
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*
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* In other words, if you pass a string to a function requiring a float,
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* it will attempt to convert the string value to a float.
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*
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* To enable strict mode, a single declare directive must be placed at the top
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* of the file.
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* This means that the strictness of typing is configured on a per-file basis.
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* This directive not only affects the type declarations of parameters, but also
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* a function's return type.
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*
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* For more info review the Concept on strict type checking in the PHP track
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* <link>.
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*
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* To disable strict typing, comment out the directive below.
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*/
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declare(strict_types=1);
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function distance(string $strandA, string $strandB): int
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{
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if (strlen($strandA) != strlen($strandB))
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throw new InvalidArgumentException('DNA strands must be of equal length.');
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$distance = 0;
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for ($i = 0; $i < strlen($strandA); $i++)
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if ($strandA[$i] != $strandB[$i]) $distance++;
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return $distance;
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}
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