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<?php |
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namespace LisPhp; |
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use RuntimeException; |
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class Parser |
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{ |
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/** |
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* @param string $input |
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* |
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* @return array |
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*/ |
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public static function parse(string $input) : array |
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{ |
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$input = static::cleanup($input); |
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$tokens = static::tokenize($input); |
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return static::readFromTokens($tokens); |
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} |
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/** |
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* @param array $tokens |
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* |
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* @return array |
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*/ |
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protected static function readFromTokens(array &$tokens) |
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{ |
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if (count($tokens) === 0) { |
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throw new RuntimeException('Unexpected EOF while reading'); |
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} |
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$token = array_shift($tokens); |
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if ($token === '(') { |
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$list = []; |
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while (count($tokens) && $tokens[0] !== ')') { |
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$list[] = static::readFromTokens($tokens); |
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} |
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if (count($tokens) && $tokens[0] === ')') { |
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array_shift($tokens); |
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} else { |
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throw new RuntimeException('Invalid syntax'); |
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} |
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return $list; |
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} elseif ($token === ')') { |
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throw new RuntimeException('Invalid syntax'); |
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} else { |
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return static::atom($token); |
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} |
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} |
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/** |
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* Splits a program into tokens. |
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* |
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* @param string $input |
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* |
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* @return array $tokens |
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*/ |
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protected static function tokenize(string $input) : array |
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{ |
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$tokens = array_filter( |
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explode( |
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' ', |
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str_replace(['(', ')'], [' ( ', ' ) '], $input) |
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), |
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function($value) { |
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return $value !== ''; |
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} |
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); |
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return $tokens; |
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} |
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/** |
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* Converts a token into an atom. |
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* |
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* @param mixed $value |
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* |
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* @return mixed |
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*/ |
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protected static function atom($value) |
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{ |
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if (is_numeric($value)) { |
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return is_float($value) ? (float) $value : (int) $value; |
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} else { |
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return $value; |
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} |
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} |
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/** |
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* Cleanups extra spaces. |
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* |
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* @param string $input |
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* |
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* @return string $input |
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*/ |
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protected static function cleanup($input) |
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{ |
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$input = preg_replace('/\s+/', ' ', $input); |
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$input = preg_replace('/\(\s+/', ' (', $input); |
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$input = preg_replace('/\s+\(/', ' (', $input); |
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$input = preg_replace('/\s+\)/', ') ', $input); |
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$input = preg_replace('/\)\s+/', ') ', $input); |
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$input = trim($input); |
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return $input; |
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} |
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} |
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fedeisas /
lisphp
