AxScript - A Simple Programming Language

AxScript is a simple programming language implemented in C++ that supports basic programming constructs. This project demonstrates the implementation of a lexer, parser, and interpreter for a custom programming language.

Features

Current features include:

• Variable declarations and initialization
• Basic arithmetic operations (+, -, *, /)
• Print statements
• Number and string literals
• User input
• Control flow
• Loops
• Error handling and recovery
• REPL (Read-Eval-Print Loop) interface

Example code:

var x = 42;
print x;
var result = x + 8;
print result;

var num;
print "Enter a number : ";
input num;
print num;

var num = 7;

compeq (num, 5) {
    print "num is equal to 5";
}

compneq (num, 5) {
    print "num is not equal to 5";
}

compge (num, 5) {
    print "num is greater than or equal to 5";
}

comple (num, 5) {
    print "num is less than or equal to 5";
}
print "end";

loop i = 1 to 5 {
    print i;
}

loop i = 5 to 1 down {
    print i;
}

Project Structure

.
├── src/
│   ├── ast.h           # Abstract Syntax Tree definitions
│   ├── environment.h   # Variable environment management
│   ├── interpreter.h   # Code interpretation logic
│   ├── lexer.cpp      # Lexical analysis implementation
│   ├── lexer.h        # Lexer header
│   ├── main.cpp       # Entry point
│   ├── parser.h       # Parser implementation
│   ├── tokens.cpp     # Token utilities
│   ├── tokens.h       # Token definitions
│   └── visitor.h      # Visitor pattern implementation

Building the Project

Prerequisites

• C++ compiler with C++11 support or later
• CMake (version 3.0 or higher)

Build Instructions

1. Clone the repository:

git clone https://github.com/sthaarwin/axscript.git
cd axscript

2. Generate build files and compile:

make all

3. Run the executable:

./src/output/axscript

Usage

Running a Script File

./axscript script.axp

Interactive Mode (REPL)

./axscript
>> print "hello world!";
hello world!

Language Syntax

Variable Declaration

var name = value;

Print Statement

print expression;

Input Statement

input variableName;

Comparison Statements

• compeq (left, right) { ... }: Executes the block if left is equal to right.
• compneq (left, right) { ... }: Executes the block if left is not equal to right.
• compge (left, right) { ... }: Executes the block if left is greater than or equal to right.
• comple (left, right) { ... }: Executes the block if left is less than or equal to right.

Example:

compeq (x, 10) {
    print "x is 10";
}

compneq (x, 10) {
    print "x is not 10";
}

compge (x, 5) {
    print "x is greater than or equal to 5";
}

comple (x, 15) {
    print "x is less than or equal to 15";
}

Loop(increment) Statement

loop var=initial-value to max-range{}

Loop(decrement) Statement

loop var=initial-value to min-range down{}

Expressions

• Arithmetic: +, -, *, /
• Numbers: Integer or floating-point
• Strings: In double quotes
• Variables: Reference by name
• Loop: loop i = 1 to 5 {}, loop i = 5 to 1 down {}

Error Handling

The interpreter provides error messages for:

• Syntax errors
• Undefined variables
• Type mismatches
• Missing semicolons
• Invalid expressions

Contributing

1. Fork the repository
2. Create a feature branch (git checkout -b feature/YourFeature)
3. Commit your changes (git commit -m 'Add some feature')
4. Push to the branch (git push origin feature/YourFeature)
5. Open a Pull Request

Future Improvements

• Control flow (comparison statements)
• Loops
• Functions
• More data types (boolean, arrays)
• Standard library
• Better error messages
• Code optimization

Acknowledgments

• Inspired by various programming language implementation tutorials and books
• Built using modern C++ features and best practices

Author

Arwin Shrestha

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Feel free to open issues or contribute to the project!