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<?php
/**
* This file is part of the MathExecutor package
*
* (c) Alexander Kiryukhin
*
* For the full copyright and license information, please view the LICENSE
* file that was distributed with this source code
*/
namespace NXP\Classes;
use NXP\Classes\Token\AbstractOperator;
use NXP\Classes\Token\InterfaceOperator;
use NXP\Classes\Token\TokenComma;
use NXP\Classes\Token\TokenFunction;
use NXP\Classes\Token\TokenLeftBracket;
use NXP\Classes\Token\TokenMinus;
use NXP\Classes\Token\TokenNumber;
use NXP\Classes\Token\TokenRightBracket;
use NXP\Classes\Token\TokenStringDoubleQuoted;
use NXP\Classes\Token\TokenStringSingleQuoted;
use NXP\Classes\Token\TokenVariable;
use NXP\Exception\IncorrectBracketsException;
use NXP\Exception\IncorrectExpressionException;
/**
* @author Alexander Kiryukhin <a.kiryukhin@mail.ru>
*/
class Lexer
{
/**
* @var TokenFactory
*/
private $tokenFactory;
public function __construct($tokenFactory)
{
$this->tokenFactory = $tokenFactory;
}
/**
* @param string $input Source string of equation
* @return array Tokens stream
*/
public function stringToTokensStream($input)
{
$matches = [];
preg_match_all($this->tokenFactory->getTokenParserRegex(), $input, $matches);
$tokenFactory = $this->tokenFactory;
$tokensStream = array_map(
function ($token) use ($tokenFactory) {
return $tokenFactory->createToken($token);
},
$matches[0]
);
return $tokensStream;
}
/**
* @param array $tokensStream Tokens stream
* @return array Array of tokens in revers polish notation
* @throws IncorrectBracketsException
*/
public function buildReversePolishNotation($tokensStream)
{
$output = [];
$stack = [];
$lastToken = null;
foreach ($tokensStream as $token) {
if ($token instanceof TokenStringDoubleQuoted) {
$output[] = $token;
} elseif ($token instanceof TokenStringSingleQuoted) {
$output[] = $token;
} elseif ($token instanceof TokenNumber) {
// if the number starts with a minus sign, it could be a negative number, or it could be an operator grabbed by the greedy regex
// if previous token is an operator or open bracket, then it negative, otherwise remove the minus sign and put a negative operator on the stack
if ($lastToken !== null) {
$value = $token->getValue();
if (($value < 0 || $this->isNegativeZero($value)) && ! ($lastToken instanceof AbstractOperator || $lastToken instanceof TokenLeftBracket)) {
$token = new TokenNumber(abs($value));
$output[] = $token;
$output[] = new TokenMinus('-');
} else {
$output[] = $token;
}
} else {
$output[] = $token;
}
} elseif ($token instanceof TokenVariable) {
$output[] = $token;
} elseif ($token instanceof TokenFunction) {
$stack[] = $token;
} elseif ($token instanceof AbstractOperator) {
// While we have something on the stack
while (($count = count($stack)) > 0
&& (
// If it is a function
($stack[$count - 1] instanceof TokenFunction)
||
// Or the operator at the top of the operator stack
// has (left associative and equal precedence)
// or has greater precedence
(($stack[$count - 1] instanceof InterfaceOperator) &&
(
($stack[$count - 1]->getAssociation() == AbstractOperator::LEFT_ASSOC &&
$token->getPriority() == $stack[$count - 1]->getPriority())
||
($stack[$count - 1]->getPriority() > $token->getPriority())
)
)
)
// And not a left bracket
&& (!($stack[$count - 1] instanceof TokenLeftBracket))) {
$output[] = array_pop($stack);
}
// Comma operators do nothing really, don't put them on the stack
if (! ($token instanceof TokenComma)) {
$stack[] = $token;
}
} elseif ($token instanceof TokenLeftBracket) {
$stack[] = $token;
} elseif ($token instanceof TokenRightBracket) {
while (($current = array_pop($stack)) && (!($current instanceof TokenLeftBracket))) {
$output[] = $current;
}
if (!empty($stack) && ($stack[count($stack) - 1] instanceof TokenFunction)) {
$output[] = array_pop($stack);
}
}
$lastToken = $token;
}
while (!empty($stack)) {
$token = array_pop($stack);
if ($token instanceof TokenLeftBracket || $token instanceof TokenRightBracket) {
throw new IncorrectBracketsException();
}
$output[] = $token;
}
return $output;
}
/**
* Check if the value is a negative zero
*
* @param int|float $x The value to check
* @return boolean True if negative zero, false otherwise
*/
private function isNegativeZero($x)
{
$floatVal = floatval($x);
return $floatVal === 0.0 && $floatVal ** -1 === -INF;
}
}
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