Custom Language Compiler

A complete compiler and interpreter for a custom statically-typed programming language, featuring lexical analysis, recursive descent parsing, semantic analysis, interpretation, and code generation to Java.

Compiler Pipeline

Source Code → Lexer → Parser → Analyzer → Interpreter (execute)
                                       └→ Generator (→ Java)

Language Features

• Types: Integer, Decimal, Boolean, Character, String, Nil
• Variables: LET name: Integer = 10; / LET CONST PI = 3.14;
• Functions: DEF add(a: Integer, b: Integer): Integer DO ... END
• Control Flow: IF/ELSE, WHILE, FOR loops
• Operators: Arithmetic (+, -, *, /), Comparison (<, >, ==, !=), Logical (&&, ||)

Example

Source:

DEF main(): Integer DO
    print("Hello, World!");
    RETURN 0;
END

Generated Java:

public class Main {
    public static void main(String[] args) {
        System.exit(new Main().main());
    }

    int main() {
        System.out.println("Hello, World!");
        return 0;
    }
}

Project Structure

src/main/java/plc/project/
├── Lexer.java        # Tokenization
├── Parser.java       # Recursive descent parser → AST
├── Ast.java          # Abstract Syntax Tree definitions
├── Analyzer.java     # Semantic analysis & type checking
├── Interpreter.java  # Tree-walking interpreter
├── Generator.java    # Java code generator
├── Environment.java  # Type system & runtime
└── Scope.java        # Variable/function scope management

Build & Test

./gradlew build    # Build project
./gradlew test     # Run test suite

Requirements: Java 11+, Gradle

Key Concepts Demonstrated

• Lexical analysis & tokenization
• LL(k) recursive descent parsing
• Abstract Syntax Tree design
• Static type checking
• Visitor design pattern
• Code generation / transpilation