Expression Parser Calculator

中文文档

A mathematical expression parser and calculator implemented in modern C++17, featuring basic arithmetic operations, operator precedence, and comprehensive error handling.

Features

• Basic arithmetic operations: +, -, *, /
• Exponentiation: ^ (right-associative)
• Parentheses for grouping: ()
• Unary operators: +, -
• Floating-point number support
• Comprehensive error handling (syntax errors, division by zero, etc.)
• Interactive command-line interface
• Cross-platform support (Windows, Linux, macOS)
• Localized interface (English and Chinese versions)

Quick Start

Download and Build

# Clone the repository
git clone https://github.com/yourusername/expr-parser-calc.git
cd expr-parser-calc

# Compile the program
g++ -std=c++17 -I include src/*.cpp -o calculator

# Run the program
./calculator

Usage Examples

Calculator> 2 + 3 * 4
Result: 14

Calculator> (2 + 3) * 4  
Result: 20

Calculator> 2^3 + 1
Result: 9

Calculator> -5 + 3.14
Result: -1.86

Project Structure

expr-parser-calc/
├── CMakeLists.txt          # CMake build configuration
├── include/                # Header files
│   ├── lexer.h            # Lexer interface
│   ├── parser.h           # Parser interface  
│   └── calculator.h       # Calculator interface
├── src/                   # Source files
│   ├── main.cpp           # Program entry point
│   ├── lexer.cpp          # Lexer implementation
│   ├── parser.cpp         # Parser implementation
│   ├── calculator.cpp     # Calculator implementation (original)
│   ├── calculator_en.cpp  # English version
│   └── calculator_zh.cpp  # Chinese version
├── test.cpp               # Unit tests
├── test_encoding.cpp      # Encoding tests
├── .gitignore             # Git ignore file
├── LICENSE                # MIT license
└── README.md              # Project documentation

Compilation and Build

Method 1: Using CMake (Recommended)

# Create build directory
mkdir build && cd build

# Generate build files
cmake ..

# Build the project
cmake --build .

# Run the program
./bin/calculator    # Linux/macOS
./bin/calculator.exe    # Windows

Method 2: Direct Compilation

Windows (PowerShell):

# Compile Chinese version
g++ -std=c++17 -I include src/main.cpp src/lexer.cpp src/parser.cpp src/calculator_zh.cpp -o calculator_zh.exe

# Compile English version
g++ -std=c++17 -I include src/main.cpp src/lexer.cpp src/parser.cpp src/calculator_en.cpp -o calculator_en.exe

# Run tests
g++ -std=c++17 -I include test.cpp src/lexer.cpp src/parser.cpp src/calculator.cpp -o test.exe
.\test.exe

Linux/macOS:

# Compile Chinese version
g++ -std=c++17 -I include src/main.cpp src/lexer.cpp src/parser.cpp src/calculator_zh.cpp -o calculator_zh

# Compile English version  
g++ -std=c++17 -I include src/main.cpp src/lexer.cpp src/parser.cpp src/calculator_en.cpp -o calculator_en

# Run tests
g++ -std=c++17 -I include test.cpp src/lexer.cpp src/parser.cpp src/calculator.cpp -o test
./test

Requirements

• Compiler: C++17 compatible compiler (GCC 7+, Clang 5+, MSVC 2017+)
• CMake: 3.10+ (optional)
• OS: Windows 10+, Linux, macOS

使用说明

启动程序后，您可以：

1. 输入数学表达式进行计算
2. 输入 help 查看帮助信息
3. 输入 quit 或 exit 退出程序

示例表达式

计算器> 2 + 3 * 4
结果: 14

计算器> (2 + 3) * 4
结果: 20

计算器> 2^3 + 1
结果: 9

计算器> -5 + 3
结果: -2

计算器> (3 + 4) * (2 - 1)
结果: 7

Technical Implementation

Lexer (Lexical Analyzer)

• Converts input strings into token sequences
• Recognizes numbers, operators, and parentheses
• Handles whitespace and floating-point numbers
• Comprehensive error detection and reporting

Parser (Syntax Analyzer)

• Recursive descent parsing algorithm
• Constructs Abstract Syntax Tree (AST)
• Proper operator precedence and associativity handling
• Supports nested parentheses and complex expressions

Calculator (Evaluation Engine)

• Traverses AST to evaluate expressions
• Complete exception handling mechanism
• Supports both interactive and batch processing modes
• Cross-platform encoding support

Operator Precedence

Precedence	Operators	Associativity	Description
1 (Highest)	()	-	Parentheses
2	+, - (unary)	Right	Unary plus/minus
3	^	Right	Exponentiation
4	*, /	Left	Multiplication/Division
5 (Lowest)	+, -	Left	Addition/Subtraction

Test Cases

The project includes a comprehensive test suite covering:

// Basic arithmetic
"2 + 3" → 5.0
"2 + 3 * 4" → 14.0  // Multiplication has higher precedence

// Parentheses grouping  
"(2 + 3) * 4" → 20.0

// Exponentiation
"2^3" → 8.0
"2^3 + 1" → 9.0

// Unary operators
"-5 + 3" → -2.0

// Floating-point arithmetic
"3.14 * 2" → 6.28

// Complex expressions
"(3 + 4) * (2 - 1)" → 7.0

Run tests:

./test    # View all test results

Error Handling

The program detects and reports the following errors:

• Invalid characters
• Syntax errors
• Division by zero
• Number format errors
• Mismatched parentheses

License

This project is licensed under the MIT License - see the LICENSE file for details.

Contributing

Issues and pull requests are welcome!

Author

AsperforMias