Crafting Interpreters

Working through Crafting Interpreters by Robert Nystrom.

The book builds two complete interpreters for Lox, a small dynamically-typed scripting language:

Part	Interpreter	Language	Approach
I	jlox	Java	Tree-walk interpreter
II	clox	C	Bytecode VM (coming later)

A Python translation of jlox (lox-python/) is maintained alongside the Java source, chapter by chapter.

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Repository Layout

crafting-interpreters/
├── src/com/craftinginterpreters/
│   ├── lox/          ← jlox source (Java)
│   └── tool/         ← code-generation utilities
├── lox-python/       ← Python translation of jlox
│   └── tests/        ← pytest test suite
├── hello.lox         ← sample Lox script
├── Makefile          ← build / run targets
└── CLAUDE.md         ← project notes & conventions

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jlox (Java)

Requirements: JDK 17+

# Compile
make compile

# Interactive REPL
make run

# Run a script
make run-file FILE=hello.lox

# Regenerate Expr.java from the grammar definition
make generate

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lox-python (Python)

Requirements: Python 3.11+

cd lox-python

# Interactive REPL
python lox.py

# Run a script
python lox.py ../hello.lox

# Run tests
python -m pytest tests/ -v

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Progress

Chapter	Topic	Java	Python
4	Scanning	✅	✅
5	Representing Code (AST)	✅	✅
6	Parsing Expressions	✅	✅
7	Evaluating Expressions	✅	✅
8	Statements and State	✅	✅
9	Control Flow
10	Functions
11	Resolving and Binding
12	Classes
13	Inheritance

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The Lox Language

Lox is a small, dynamically-typed language with:

• Arithmetic, comparison, and logical operators
• Variables (var), control flow (if, while, for)
• Functions (fun) and closures
• Classes and inheritance

var x = 1 + 2.5;
print x;