search
HomeBackend DevelopmentPHP TutorialAn in-depth analysis of the interpreter pattern of PHP design patterns_PHP tutorial

Interpreter mode, which consists of a grammar representation with a composite class hierarchical structure. The rules are mapped to classes. The expressions following the grammar can be converted into an abstract syntax tree, except for the composite mode. There is nothing other than the instance object graph.

Tree is an abstract noun, because in fact most of the time it is an abstract representation of an expression, which ignores that there may be a string or a concrete expression of a data structure, (for example, in PHP , "A" and "x41" are different concrete manifestations of the same abstract literal value), and the results are decoupled through logical rules, greatly simplifying the interpretation process.

Interpreter is not a very common pattern, but for simple syntaxes, it is as easy to add a rule as adding a class, but it does not solve the conversion from concrete representation to abstract syntax tree, which is done by other services Completed.

The Interpreter pattern is designed to leverage a composite hierarchical structure for a simple AbstractExpression method (interpreter operation). The parameters of the interpreter operation are usually collectively called the context. For a given method , they are often replaced by calculated values, or they may not exist for some operations.

Likewise, when an interpreter is included, the leaf and container participants of a composite pattern have different names, reflecting the role they play: terminal or nonterminal expressions.

Participants:
◆Client: Use explain operation.
◆Abstract Expression: Abstract based on an expression tree.
◆NonTerminalExpression: An expression that recursively contains other abstract expressions (AbstractExpression instances).
◆Terminal Expression: An expression that cannot be further simplified.


The book "Design Patterns" provides an extended example for this pattern. I remodeled it by replacing the Boolean expression with a mathematical expression, so this example solves a mathematical expression. expression, its evaluate() is separated into a different ConcreteExpression class.

Copy code The code is as follows:

/** 
 * AbstractExpression. All implementations of this interface 
 * are ConcreteExpressions. 
 */
interface MathExpression 

    /** 
     * Calculates the value assumed by the expression. 
     * Note that $values is passed to all expression but it 
     * is used by Variable only. This is required to abstract 
     * away the tree structure. 
    */
    public function evaluate(array $values); 


/** 
 * A terminal expression which is a literal value. 
 */
class Literal implements MathExpression 

    private $_value; 

    public function __construct($value) 
    { 
        $this->_value = $value; 
    } 

    public function evaluate(array $values) 
    { 
        return $this->_value; 
    } 


/** 
 * A terminal expression which represents a variable. 
 */
class Variable implements MathExpression 

    private $_letter; 

    public function __construct($letter) 
    { 
        $this->_letter = $letter; 
    } 

    public function evaluate(array $values) 
    { 
        return $values[$this->_letter]; 
    } 


/** 
 * Nonterminal expression. 
 */
class Sum implements MathExpression 

    private $_a; 
    private $_b; 

    public function __construct(MathExpression $a, MathExpression $b) 
    { 
        $this->_a = $a; 
        $this->_b = $b; 
    } 

    public function evaluate(array $values) 
    { 
        return $this->_a->evaluate($values) + $this->_b->evaluate($values); 
    } 


/** 
 * Nonterminal expression. 
 */
class Product implements MathExpression 

    private $_a; 
    private $_b; 

    public function __construct(MathExpression $a, MathExpression $b) 
    { 
        $this->_a = $a; 
        $this->_b = $b; 
    } 

    public function evaluate(array $values) 
    { 
        return $this->_a->evaluate($values) * $this->_b->evaluate($values); 
    } 


// 10(a + 3) 
$expression = new Product(new Literal(10), new Sum(new Variable('a'), new Literal(3))); 
echo $expression->evaluate(array('a' => 4)), "n"; 
// adding new rules to the grammar is easy: 
// e.g. Power, Subtraction... 
// thanks to the Composite, manipulation is even simpler: 
// we could add substitute($letter, MathExpression $expr) 
// to the interface...

www.bkjia.comtruehttp://www.bkjia.com/PHPjc/327555.htmlTechArticle解释器(Interpreter)模式,它包括一个具有复合类分层结构的文法表现,规则是映射到类,跟随在文法后面的表达式可以被转换成一个抽象...
Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
The Continued Use of PHP: Reasons for Its EnduranceThe Continued Use of PHP: Reasons for Its EnduranceApr 19, 2025 am 12:23 AM

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python: Exploring Their Similarities and DifferencesPHP and Python: Exploring Their Similarities and DifferencesApr 19, 2025 am 12:21 AM

PHP and Python are both high-level programming languages ​​that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP and Python: Different Paradigms ExplainedPHP and Python: Different Paradigms ExplainedApr 18, 2025 am 12:26 AM

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP and Python: A Deep Dive into Their HistoryPHP and Python: A Deep Dive into Their HistoryApr 18, 2025 am 12:25 AM

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

Choosing Between PHP and Python: A GuideChoosing Between PHP and Python: A GuideApr 18, 2025 am 12:24 AM

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP and Frameworks: Modernizing the LanguagePHP and Frameworks: Modernizing the LanguageApr 18, 2025 am 12:14 AM

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHP's Impact: Web Development and BeyondPHP's Impact: Web Development and BeyondApr 18, 2025 am 12:10 AM

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

How does PHP type hinting work, including scalar types, return types, union types, and nullable types?How does PHP type hinting work, including scalar types, return types, union types, and nullable types?Apr 17, 2025 am 12:25 AM

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values ​​and handle functions that may return null values.

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Tools

SublimeText3 English version

SublimeText3 English version

Recommended: Win version, supports code prompts!

Dreamweaver Mac version

Dreamweaver Mac version

Visual web development tools

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function