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How Can I Build a PHP Calculator Using the Shunting Yard Algorithm?
How Can I Build a PHP Calculator Using the Shunting Yard Algorithm?
Dec 06, 2024 am 08:48 AM
How to Create a Calculator Using PHP
Problem:
You want to develop a PHP calculator that evaluates simple algebraic expressions inputted by users in standard notation, displaying the evaluation process. The challenge lies in efficiently calculating the expression's value.
Answer:
Consider utilizing the Shunting Yard Algorithm for its simplicity and efficiency in evaluating algebraic expressions.
Shunting Yard Algorithm Implementation
Expression Definitions:
Create classes to represent different elements of the expression, such as parentheses, numbers, operators, and so on:
class Parenthesis extends TerminalExpression { ... }
class Number extends TerminalExpression { ... }
class Addition extends Operator { ... }
class Subtraction extends Operator { ... }
class Multiplication extends Operator { ... }
class Division extends Operator { ... }
class Power extends Operator { ... }
Stack Implementation:
class Stack {
protected $data = array();
// ... Methods for pushing, popping, and peeking from the stack ...
}
Executor Class:
The executor class parses the expression using the Shunting Yard algorithm and evaluates it:
class Math {
// ... Fields and methods for parsing, running, and evaluating the expression ...
}
Example:
Here's an example of how to use the calculator:
$math = new Math();
$answer = $math->evaluate('(2 + 3) * 4');
var_dump($answer);
// int(20)
$answer = $math->evaluate('1 + 2 * ((3 + 4) * 5 + 6)');
var_dump($answer);
// int(83)
This example covers grouping and operator precedence. However, you can customize the implementation to suit your specific requirements.
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