Simple instructions let Cursor generate high-quality code

1. How to generate high-quality code using simple instructions

Tools such as Cursor/Windsurf/Augment/RooCode/Cline can quickly generate code, but how to ensure that the code is simple, reliable, and easy to maintain? We can use the following simple instructions to achieve the effect.

The command prompt is as follows:

You are an excellent technical architect and programmer. When performing architecture analysis, functional module analysis, and coding, please follow the following rules:
1. Follow the "first principles" when analyzing problems, technical architecture, code module combinations, etc.
2. When coding, please follow the "DRY principle", "KISS principle", "SOLID principle", and "YAGNI principle"
3. If a single class, function or code file exceeds 500 lines, please identify, decompose and separate it. Follow the above principles in the process of identification, decomposition and separation.

The most important things in the entire instruction are: the first principle, the "DRY principle", the "KISS principle", the "SOLID principle", and the "YAGNI principle"

These methodologies summarized by outstanding predecessors are the core cornerstones, making it easier for large AI models to understand your goals and requirements.

It seems like such a simple instruction, but what is its main purpose? We need to analyze the underlying logic of these principles one by one.

2. The underlying principles of these principles

"First Principles" | Methodology for Analyzing Problems

Most of us are accustomed to using the inductive method. The "first principles" is a methodology for analyzing problems that is different from the "inductive method".

First-Principles Thinking is a way of thinking that returns to the essence of things. It advocates starting from the most basic and irreducible truths or physical laws, and deriving solutions through logical deduction rather than relying on experience or analogical reasoning.

1. 1.  Core Definition

Essence tracing: Break down the problem to its most basic physical or logical foundation (such as quantum mechanics equations, mathematical axioms, etc.) and reconstruct the solution.

Origin of philosophy: Aristotle in Metaphysics

” It is proposed that there is a basic proposition that cannot be violated in every system.

Modern applications: widely known due to Elon Musk's practice (such as SpaceX rocket cost optimization, Tesla battery design). Corresponding to the computability boundary of computer science, such as the CAP theorem in the distributed field, it has become the first principle of architecture design. Google reconstructed GFS based on the basic theory of distributed systems, and the Rust language designed the ownership model based on the physical characteristics of memory.

1. 2.  Key Features

Deductive reasoning: logical deduction from basic assumptions rather than induction (such as the observation that all plant cells have a nucleus).

Interdisciplinarity: Applicable to fields such as physics, economics, and law (such as the essential characteristics that distinguish fraud from theft in criminal law).

Anti-empiricism: Rejecting the inertia of thinking that “industry practice” or “it has always been this way”.

1. 3.  Difference from induction

1. 4.  Application in Computer

Architecture design :

• Cloud native scheduling system : Designing container orchestration strategies based on quantum decoherence theory to break through the limitations of traditional time slice rotation
• Database engine : Reconstruct the WAL log mechanism based on the law of entropy increase to achieve physical-level crash consistency

Development paradigm :

• Microservice governance : replacing empirical circuit breaker thresholds with network topology manifold analysis
• AI Engineering : Designing Model Service Grid Based on Information Bottleneck Theory

Protocol Innovation :

• Blockchain consensus : Reconstructing the BFT algorithm based on relativistic space-time constraints
• Edge computing : deriving node communication topology from Maxwell's equations

1. 5.  Limitations

High computing cost: For example, first-principles calculations in quantum mechanics require a lot of computing power.

Difficulty of abstraction: Complex problems (such as social phenomena) are difficult to break down to their essential level.

Risk of oversimplification: nonlinear or chaotic factors in reality may be ignored.

DRY - Don't Repeat Yourself | Software Development Principles

The DRY (Don't Repeat Yourself) principle is a core design principle in software development. It literally means "Don't repeat yourself". Its core idea is that every function or logic of the system should have only one clear implementation to avoid code or information redundancy. The following is a key analysis:

1.  Core Definition

Uniqueness : Each function/logic should be implemented only once in the system, and when repeated, it should be abstracted into a reusable module (such as function, class, service).

Source : First proposed in "The Programmer's Cultivation", emphasizing reducing duplication through abstraction.

2.  Core Values

Maintainability : When modifying the logic, only one place needs to be adjusted, reducing the risk of errors.

Readability : Reduce redundant code and improve structural clarity.

Consistency : Ensure that the same functionality behaves in the same way.

3.  Common application scenarios

Code reuse : Encapsulate repeated logic into functions or tool classes (such as user login verification and data conversion).

Data management : Avoid storing duplicate data and ensure a single source of data.

Centralized configuration : Use configuration files instead of hard coding.

4.  Pitfalls to watch out for

Over-abstraction : Premature abstraction increases complexity without explicit repetitive requirements.

Ignoring context : seemingly repetitive code may need to be implemented independently due to business differences (e.g., similar validation rules but different subsequent extensions).

Disposable code : Hard coding or copying and pasting may not seem repetitive, but it actually increases maintenance costs.

5.  Relationship with other principles

KISS/YAGNI : DRY pursues reuse, but needs to balance simplicity (KISS) and "don't over-design" (YAGNI).

Single responsibility : Avoid combining functions for reuse, which leads to mixed responsibilities.

The essence of the DRY principle is to improve efficiency through reasonable abstraction, rather than mechanically eliminating duplication. In practice, it is necessary to judge whether there is duplication based on the specific context and weigh the cost and benefit of abstraction.

The KISS (Keep It Simple, Stupid) principle is a core design principle widely used in engineering design, software development and other fields. Its core idea is to improve the reliability, maintainability and user experience of the system by simplifying the design. The following is a key analysis:

KISS - Keep It Simple | Software Development Principles

1.  Core Definition

Literal translation : "Keep It Simple, Stupid", emphasizing that the design should be as simple and clear as possible, avoiding unnecessary complexity .

It was proposed by Lockheed engineer Kelly Johnson (designer of the U-2 reconnaissance aircraft), who originally required that the tool design must be easy for ordinary mechanics to repair.

2.  Core Values

Reduce complexity : Simple designs are easier to understand, debug, and maintain, reducing the error rate.

Improve efficiency : reduce development time and resource consumption, and avoid over-design.

Optimize the experience : In user experience (such as product design), simplicity is directly related to ease of use.

3.  Practical suggestions

Code level :

Design level :

Communication and Management :

4.  Common Misunderstandings

Don't confuse it with simplicity : simplicity does not mean lack of functionality, but rather efficiency is achieved through reasonable abstraction.

Premature optimization : Avoid adding complexity for "possible future needs" (see the YAGNI principle).

Ignoring context : You need to balance simplicity with practical needs (e.g., high-performance scenarios may require specific optimizations).

5.  Relationship with other principles

And Occam's razor : Both advocate simplicity, but KISS focuses on ** method implementation **, while Occam's razor focuses on ** theoretical assumptions **.

And the DRY principle : DRY solves code duplication, KISS solves over-design, the two complement each other.

The essence of the KISS principle is to simplify complexity and build a more robust system by focusing on core requirements and reducing unnecessary complexity. Its application needs to be combined with specific scenarios to avoid mechanical simplification.

SOLID - Five Principles of Object-Oriented Programming | Software Development Principles

The SOLID principles are five core principles of object-oriented programming and design, which aim to improve the maintainability, flexibility, and extensibility of code . They were summarized and promoted by Robert C. Martin (Uncle Bob) in the early 2000s and originated from object-oriented practices in the 1980s.

1.  Single Responsibility Principle (SRP)

Definition : A class should have only one reason to change, that is, it should be responsible for only one function.

Purpose : Reduce complexity and improve code readability and testability.

Example : Split user data storage and retrieval into two separate classes ( UserSaver  and  UserRetriever ).

2.  Open/Closed Principle (OCP)

Definition : Software entities should be open for extension but closed for modification. New functionality should be implemented through abstraction and polymorphism rather than modifying existing code.

Function : Reduce modification risks and improve system stability.

Example : Use abstract classes or interfaces to extend the tax calculation logic instead of directly modifying the original calculation class.

3.  Liskov Substitution Principle (LSP)

Definition : A subclass must be able to replace a parent class without violating program correctness.

Function : Ensure the rationality of inheritance relationship and enhance code predictability.

Example : When the Square class inherits the Rectangle class, the area calculation logic must be consistent.

4.  Interface Segregation Principle (ISP)

Definition : A client should not depend on interfaces it does not need. Interfaces should be designed to be small and specialized.

Function : Reduce redundant dependencies and improve flexibility.

Example : Split the large "user operation interface" into a "login interface" and a "registration interface".

5.  Dependency Inversion Principle (DIP)

Definition : High-level modules should not depend on low-level modules, both should depend on abstractions.

Function : Reduce coupling and facilitate testing and expansion.

Example : Abstracting database operations into interfaces via dependency injection (DI).

Core Values

Maintainability : Reduce modification costs through modular design.

Extensibility : Supports flexible addition of new features.

Reusability : Code with high cohesion and low coupling is easier to reuse.

Practical Application

It is still applicable in microservices and cloud-native architectures. For example, SRP guides the single-function design of microservices, and DIP supports dependency injection decoupling.

Following the SOLID principles can significantly improve code quality, but it is necessary to combine actual scenarios to avoid over-design (such as the YAGNI principle).

YAGNI - You Aren't Gonna Need It | Software Development Principles

The YAGNI (You Ain't Gonna Need It) principle is a core practice in software development, emphasizing that only the functions that are clearly needed at the moment should be implemented to avoid over-design and premature optimization .

1.  Core idea

Focus on the present : only implement current needs and do not predict functions that may be used in the future.

Avoid waste : Reduce the time and resources wasted on writing unproven features.

2.  Core Values

Simplify code : reduce complexity and maintenance cost.

Improve efficiency : Focus resources on solving practical problems and speed up delivery.

Flexible Adaptability : It is easier to adjust when requirements change and avoid being bound by redundant code.

3.  Difference from KISS principle

YAGNI : Solve the "should you do it or not" problem (avoid implementing features that are not currently needed).

KISS : Solve the “how to do it” (implement the current function in the simplest way).

4.  Common application scenarios

Avoid over-design : For example, the system currently only needs Redis storage configuration, and there is no need to implement ZooKeeper support in advance (but extension points need to be reserved).

Reject redundant dependencies : Do not introduce unused third-party libraries in advance.

5.  Potential Pitfalls

Ignoring architecture : There is a need to balance “not over-engineering” with keeping the code scalable (such as following SOLID principles).

Ignore non-functional requirements : performance, security, etc. still need to be considered in advance.

6.  Practical suggestions

Requirements verification : Clarify the priority of core requirements and avoid development based on speculation.

Continuous iteration : gradually improve functions through user feedback rather than over-designing at one time.

The YAGNI principle advocates ** development driven by actual needs **. It is a pragmatic agile practice that needs to be flexibly applied in the context of the project.

3. Put these principles into practice in software development

Assuming we need a program implementation that also uses the system, we follow these principles to generate the corresponding implementation:

 The sample code generated in accordance with  the first principle, "DRY principle", "KISS principle", "SOLID principle" and "YAGNI principle" is as follows:

package  main
import  (
    "fmt"
)

// User interface, follow the single responsibility principle and the open-closed principle
type  User  interface  {
    GetID()  int
    GetName()  string
    GetEmail()  string
}

//Specific user structure
type  ConcreteUser  struct  {
    id     int
    name   string
    email  string
}

func (u *ConcreteUser)   GetID()  int  {
    return  u.id
}

func (u *ConcreteUser)   GetName()  string  {
    return  u.name
}

func (u *ConcreteUser)   GetEmail()  string  {
    return  u.email
}

// User management interface, follow the interface isolation principle
type  UserManager  interface  {
    AddUser(user User)
    GetUserByID(id  int ) User
    GetAllUsers() []User
}

// Specific user management structure
type  ConcreteUserManager  struct  {
    users  map [ int ]User
}

// Factory function to create user management instance, following the DRY principle
func NewConcreteUserManager ()   *ConcreteUserManager {
    return  &ConcreteUserManager{
        users:  make ( map [ int ]User),
    }
}

func (um *ConcreteUserManager)   AddUser(user User) {
    um.users[user.GetID()] = user
}

func (um *ConcreteUserManager)   GetUserByID(id  int ) User {
    return  um.users[id]
}

func (um *ConcreteUserManager)   GetAllUsers() []User {
    var  allUsers []User
    for  _, user :=  range  um.users {
        allUsers =  append (allUsers, user)
    }
    return  allUsers
}

// Function to print user information, following the KISS principle
func printUserInfo (user User)   {
    fmt.Printf( "User ID: %d, Name: %s, Email: %s\n" , user.GetID(), user.GetName(), user.GetEmail())
}

// Main function, showing the usage of functions
func main ()   {
    // Create a user management instance
    userManager := NewConcreteUserManager()

    // Create a user
    user1 := &ConcreteUser{
        id:     1 ,
        name:   "Alice" ,
        email:  "alice@example.com" ,
    }
    user2 := &ConcreteUser{
        id:     2 ,
        name:   "Bob" ,
        email:  "bob@example.com" ,
    }

    // Add users to the user management system
    userManager.AddUser(user1)
    userManager.AddUser(user2)

    // Get a single user's information
    retrievedUser := userManager.GetUserByID( 1 )
    if  retrievedUser !=  nil  {
        printUserInfo(retrievedUser)
    }

    // Get all user information
    allUsers := userManager.GetAllUsers()
    fmt.Println( "All user information:" )
    for  _, user :=  range  allUsers {
        printUserInfo(user)
    }
}    

The following is a user system code example written in Go language, showing how to follow the "first principle", "DRY principle", "KISS principle", "SOLID principle" and "YAGNI principle".

First Principles

• Essential tracing : Starting from the most basic concepts of the user system, "user" and "user management", we defined the user interface and user management interface, which are the core logical basis of the user system. Just like building a solution from the most basic laws of physics, we deduce the functions of the entire system based on these basic concepts.
• Deductive approach : First define the abstract interface, then gradually implement the specific structure and methods, and deduce specific functions from the basic abstract concepts. For example, deduce the implementation of a specific user structure from the user interface.

DRY principle

• Uniqueness : The factory function NewConcreteUserManager for creating a user management instance   avoids repeating the logic of creating a user management instance in multiple places, encapsulates the creation logic in one function, and realizes code reuse.

KISS principle

• Simple design : The printUserInfo function for printing user information   is very simple and direct. It directly obtains user information and prints it without complex nested logic, which meets the requirement of keeping it simple in the KISS principle.

SOLID principles

• Single Responsibility Principle (SRP) : The user interface  User  is only responsible for defining the user's basic attributes and methods, the user management interface  UserManager  is only responsible for managing user addition, acquisition and other operations, and each class or interface is only responsible for one function.
• Open-Closed Principle (OCP) : The User interface  provides  an open interface for subsequent extension of new user types without modifying the existing code. For example, if you want to add a new user type, you only need to implement  the User  interface.
• Liskov Substitution Principle (LSP) : If new user types implement  the User  interface, then these new user types can completely replace the original user types without affecting the normal operation of the system.
• Interface Segregation Principle (ISP) : The user management interface  UserManager  only contains necessary methods. The client only needs to rely on the methods it needs in this interface, avoiding dependence on unnecessary interfaces.
• Dependency Inversion Principle (DIP) : The user management structure  ConcreteUserManager  depends on the user interface  User , rather than the specific user structure, which reduces the coupling between the user management structure and the specific user implementation.

YAGNI principle

• Focus on the present : In the code, we only implemented the functions that are clearly needed at the moment, such as adding users, obtaining single user information, and obtaining all user information. We did not write code in advance for possible future needs, thus avoiding over-design.

IV. Conclusion

When generating code with the help of AI tools such as Cursor and Windsurf, incorporating methodologies such as ** first principles, DRY, KISS, SOLID, YAGNI ** into instructions can effectively improve code quality.

As a core thinking framework, the first principle conducts logical deduction based on the essence of the problem, helping to break through the limitations of experience and find more innovative solutions;

The DRY principle enhances code reusability and maintainability by eliminating duplicate logic;

The KISS principle emphasizes keeping the design simple and reducing system complexity;

The SOLID principle systematically improves the scalability, maintainability, and reusability of code from the perspective of object-oriented programming;

The YAGNI principle focuses on current needs, avoids over-design, and ensures efficient use of resources.

It can be seen from the Go language practice cases in user systems that these principles do not exist in isolation, but complement each other.

For example, the essential concepts of users and user management are abstracted based on the first principles, and then the SOLID principles are used to build interfaces and structures. At the same time, code reuse is achieved through the DRY principle, functional implementation is simplified through the KISS principle, and functional boundaries are constrained by the YAGNI principle.

Following these principles will not only make the AI-generated code more in line with engineering standards, but also bring higher reliability, maintainability and development efficiency to software development, becoming an important cornerstone for guiding the production of high-quality code.