🌲 Determa Programming Language

• A statically-typed language, custom compiler, and virtual machine — written entirely in C

Version: v0.3 “Spruce”
Status: Active Development

Determa is a full programming language built completely from scratch in C — including its own lexer, parser, type system, bytecode compiler, virtual machine, and garbage collector.

Designed as a capstone project for Theoretical Computer Science, Determa merges concepts from formal languages (DFA, CFG, Scope Theory) with practical systems implementation (interpreters, memory management, call stacks, symbol tables).

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🚀 Key Features (Current Implementation)

🔹 1. Deterministic Finite Automata (Lexer)

• High-performance tokenization
• Zero external dependencies
• Supports identifiers, keywords, integers, booleans, strings, operators, and punctuation

🔹 2. Recursive Descent Parser (Pushdown Automaton)

• Builds a complete Abstract Syntax Tree (AST)
• Implements full statement/expression grammar
• Supports:
  • Variable declarations
  • Blocks
  • If / While
  • Function declarations & calls
  • Return statements
  • Binary and unary operators

🔹 3. Static Type Checker

• Validates:
  • Type consistency in expressions
  • Variable usage and declarations
  • Function signatures & arity
• Persistent Symbol Table
• Proper lexical scope checking (blocks, functions)

🔹 4. Bytecode Compiler

• Converts AST → custom bytecode instruction set
• Implements:
  • Global & local variable access
  • Arithmetic & logic ops
  • Conditional jumps
  • Loops
  • Function call conventions
  • Stack-based execution model

🔹 5. Stack-Based Virtual Machine

• Registers:
  • Operand stack
  • Call frames
  • Instruction pointer
• OpCode support:
  • OP_ADD, OP_SUB, OP_MULTIPLY, OP_DIVIDE, OP_MODULO
  • OP_GET_LOCAL, OP_SET_LOCAL
  • OP_GET_GLOBAL, OP_SET_GLOBAL
  • OP_CALL, OP_RETURN
  • OP_JUMP, OP_JUMP_IF_FALSE, OP_LOOP
  • OP_PRINT, OP_POP
• Deterministic function call model
• Correct stack unwinding + return value propagation

🔹 6. Automatic Garbage Collector

• Mark-and-Sweep GC
• Heaps manages:
  • Strings
  • Functions
  • Future object types
• Safe during compilation (compiler roots marked)

🔹 7. REPL + Script Execution

• Interactive shell with persistent variables
• Execute .det scripts directly
• Optional parser-trace debug mode (PDA visualization)

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🧩 Project Architecture

Source Code
   ↓
Lexer (DFA)
   ↓
Parser (Recursive Descent → AST)
   ↓
Type Checker (Static Analysis)
   ↓
Compiler (Bytecode Generation)
   ↓
Virtual Machine (Stack-Based Execution)
   ↓
Output

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📦 Quick Start

Build

# Windows
./build.bat

Outputs:

• bin/determa.exe → language runner + REPL
• bin/determa_test.exe → full unit test suite

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💻 Usage Examples

1. REPL

$ .bin\determa.exe
Determa v0.2 'Cedar'
> var x = 10;
> var y = 20;
> print x + y * 2;
Out: 50

2. Script Execution

Executing examples/fibonacci.det

func fib(n) : int {
    if n == 0 {
        return 0;
    } elif n == 1 {
        return 1;
    } else {
        return fib(n - 1) + fib(n - 2);
    }
}

print "Fibonacci Sequence (just fib(10)):";
print fib(4);

Run:

$.bin\determa.exe examples/hello.det

3. PDA Debug Mode

$ .bin\determa.exe --pda-debug
> 1 + 2;
PUSH: Expression
  PUSH: Term
    PUSH: Factor

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📋 Component Status

Phase	Component	Status	Details
I	Lexer	✅ Complete	DFA tokenizer
II	Parser	✅ Complete	AST construction
III	Type Checker	✅ Complete	Symbol tables, scopes
IV	Virtual Machine	✅ Complete	Custom ISA & stack machine
V	Garbage Collector	✅ Complete	Mark-and-sweep
VI	Control Flow	✅ Complete	If, while, logical ops
VII	Functions	🏗️ In Progress	Calls, local vars, returns
VIII	Closures	🔜 Planned	Lexical captures

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🛠️ Tech Stack

• Language: C (C99)
• Architecture: Hand-written compiler + VM
• Dependencies: None (0 external libraries)
• Memory: Custom GC
• Design Inspiration: Wren, Lox, Lua, JVM bytecode

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🌿 Philosophy

“Strong like the wood it's named after.”

Determa emphasizes:

• Clarity
• Predictability
• Theory-meets-systems design
• Fully self-implemented infrastructure

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👨‍💻 Author

Andrew Fernandes

Feel free to ⭐ star the repository or reach out on LinkedIn!