README

Used shunting-yard algorithm to convert any expressions to RPN(Reverse Polish Notations) and process it.

• Installation
• Predefined parsers
  • Arithmetical
  • Logical
• Extending
• Custom parser
• Operators
  • Types
  • Reserved names
• Callbacks
• References

Installation

composer require zippovich2/expressions-parser

Predefined parsers

Arithmetical expressions parser

use Zippovich2\ExpressionsParser\Parser\ArithmeticalParser;

$parser = new ArithmeticalParser();

// 45
$parser->eval('2 + (3^3) + 8 * (3 - 1)'); 

// 3.0001220703125
$parser->eval('3 + 4 * 2 / (1 - 5) ^ 2 ^ 3'); 

// 58
$parser->eval('58+(max(1, 2, 3)/3)'); 

Logical expressions parser

use Zippovich2\ExpressionsParser\Parser\LogicalParser;

$parser = new LogicalParser();

// true
$parser->eval('true || false'); 

// false
$parser->eval('true && false'); 

// true
$parser->eval('true xor false'); 

// false
$parser->eval('true xor true'); 

Extending

use Zippovich2\ExpressionsParser\Parser\LogicalParser;
use Zippovich2\ExpressionsParser\OperatorFactory;

$parser = new LogicalParser();
$parser->addOperator(OperatorFactory::rightAssociative('**', function($a, $b){
    return $a ** $b;
}, 5));
$parser->addOperator(OperatorFactory::func('if', function($condition, $if, $else){
    return $condition ? $if : $else;
}));
$parser->addOperator(OperatorFactory::constant('e', M_E));

// false
$res = $parser->eval('if(2 < 1, true, false)');

// true
$res = $parser->eval('if(2 > 1, true, false)');

// 16
$res = $parser->eval('2**4');

// 3.718281828459
$res = $parser->eval('e+1');

Custom parser

use Zippovich2\ExpressionsParser\Parser;
use Zippovich2\ExpressionsParser\OperatorsList;
use Zippovich2\ExpressionsParser\OperatorFactory;

$operators = new OperatorsList();

$operators->add(OperatorFactory::leftAssociative('AND', function ($a, $b){
    return $a && $b;
}));

$parser = new Parser($operators);

// false
$parser->eval('1 AND 0');

// true
$parser->eval('1 AND 0');

Operators

Types

1. Operator::TYPE_LEFT_ASSOCIATIVE - left associative.
2. Operator::TYPE_RIGHT_ASSOCIATIVE - right associative.
3. Operator::TYPE_FUNCTION - function.
4. Operator::TYPE_LEFT_ASSOCIATIVE - constant.

Reserved names

An operator cannot be created using the characters ( and ) because it is used for groups and , because it is used for separating function parameters.

Callbacks

You can provide callback for each operator or create global callback to handle all operators.

use Zippovich2\ExpressionsParser\Parser;
use Zippovich2\ExpressionsParser\OperatorsList;
use Zippovich2\ExpressionsParser\OperatorFactory;

$operators = new OperatorsList();

$operators->add(OperatorFactory::leftAssociative('AND', function ($a, $b){
    return $a && $b;
}));

$operators->add(OperatorFactory::leftAssociative('OR'));

$defaultCallback = function ($operator, ...$parameters){
    switch ($operator){
        case 'OR':
            return $parameters[0] || $parameters[1];
    }
    
    throw new \LogicException('This code should not be reached.');
};

$parser = new Parser($operators);

// true
$parser->eval('1 AND 0 OR 1', $defaultCallback);

// false
$parser->eval('1 AND 0 OR 0', $defaultCallback);

/**
 * @throws \LogicException because no callback was provided for "OR" operator. 
 */
$parser->eval('1 AND 0 OR 0');

References

• Shunting-yard algorithm
• Operator
• Operator associativity
• Order of operations or operator precedence
• Reverse Polish notation