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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\TokenNumber;
use NXP\Classes\Token\TokenRightBracket;
use NXP\Exception\IncorrectBracketsException;
use NXP\Exception\IncorrectExpressionException;
/**
* @author Alexander Kiryukhin <alexander@symdev.org>
*/
class Lexer
{
/**
* @var TokenFactory
*/
private $tokenFactory;
public function __construct($tokenFactory)
{
$this->tokenFactory = $tokenFactory;
}
/**
* @param string $input Source string of equation
* @return array Tokens stream
* @throws \NXP\Exception\IncorrectExpressionException
*/
public function stringToTokensStream($input)
{
$matches = array();
preg_match_all($this->tokenFactory->getTokenParserRegex(), $input, $matches);
$tokensStream = array_map(
function ($token) {
return $this->tokenFactory->createToken($token);
},
$matches[0]
);
return $tokensStream;
}
/**
* @param array $tokensStream Tokens stream
* @return array Array of tokens in revers polish notation
* @throws \NXP\Exception\IncorrectExpressionException
*/
public function buildReversePolishNotation($tokensStream)
{
$output = array();
$stack = array();
foreach ($tokensStream as $token) {
if ($token instanceof TokenNumber) {
$output[] = $token;
}
if ($token instanceof TokenFunction) {
array_push($stack, $token);
}
if ($token instanceof TokenLeftBracket) {
array_push($stack, $token);
}
if ($token instanceof TokenComma) {
while (($current = array_pop($stack)) && (!$current instanceof TokenLeftBracket)) {
$output[] = $current;
if (empty($stack)) {
throw new IncorrectExpressionException();
}
}
}
if ($token instanceof TokenRightBracket) {
while (($current = array_pop($stack)) && (!$current instanceof TokenLeftBracket)) {
$output[] = $current;
}
if (!empty($stack) && ($stack[count($stack)-1] instanceof TokenFunction)) {
$output[] = array_pop($stack);
}
}
if ($token instanceof AbstractOperator) {
while (
count($stack) > 0 &&
($stack[count($stack)-1] instanceof InterfaceOperator) &&
(
$token->getAssociation() == AbstractOperator::LEFT_ASSOC &&
$token->getPriority() <= $stack[count($stack)-1]->getPriority()
) || (
$token->getAssociation() == AbstractOperator::RIGHT_ASSOC &&
$token->getPriority() < $stack[count($stack)-1]->getPriority()
)
) {
$output[] = array_pop($stack);
}
array_push($stack, $token);
}
}
while (!empty($stack)) {
$token = array_pop($stack);
if ($token instanceof TokenLeftBracket || $token instanceof TokenRightBracket) {
throw new IncorrectBracketsException();
}
$output[] = $token;
}
return $output;
}
}
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