Introduction - Ruchy Notebook - Language Proof
Description: Step-by-step empirical proof that all 41 Ruchy language features work in the notebook

# Introduction: Empirical Language Proof

## Why This Book Exists

This is not a typical language tutorial. This is an empirical proof that Ruchy works.

Every feature documented here has:

- ✅ Runnable code you can copy into the notebook
- ✅ Expected output you can verify
- ✅ Automated tests proving it works
- ✅ Coverage reports proving tests are thorough
- ✅ Mutation tests proving tests catch real bugs
- ✅ E2E tests proving it works in browsers

## The Promise

If you can run this code in the Ruchy notebook and get the expected output, the language feature works.

No hand-waving. No "coming soon." No "should work."

Just: Here's the code, here's the output, here's the test that proves it.

## How to Use This Book

### 1. Run the Notebook

    # Start the notebook server
    cargo run --features notebook --bin ruchy notebook

    # Or open the web version
    open http://localhost:8000/notebook.html

### 2. Try Each Feature

Copy the code from each chapter into the notebook. Run it. Verify the output matches.

### 3. Check the Proof

Every chapter links to:

- The automated test file
- The coverage report
- The mutation test results
- The E2E test

If you don't trust the docs, check the tests.

## Quality Standards

This book and the notebook are held to wasm-labs EXTREME quality standards:

### Coverage Requirements

- ✅ Line Coverage: ≥85%
- ✅ Branch Coverage: ≥90%
- ✅ Mutation Score: ≥90%

### Testing Requirements

- ✅ Unit Tests: Every function
- ✅ Property Tests: 10,000+ random inputs
- ✅ Mutation Tests: Empirical bug-catching proof
- ✅ E2E Tests: Real browsers (Chrome, Firefox, Safari)

### WASM Requirements

- ✅ Size: <500KB
- ✅ Purity: 0 WASI imports
- ✅ Validation: Deep bytecode inspection

## The 41 Features

This book proves all 41 Ruchy language features work in the notebook:

### Foundation (9 features)

1. Integer/Float/String/Bool/Nil literals
2. Variable binding and assignment
3. Comments (line and block)
4. Arithmetic operators (+, -, *, /, %)
5. Comparison operators (<, >, <=, >=, ==, !=)
6. Logical operators (&&, ||, !)
7. Bitwise operators (&, |, ^, <<, >>)
8. If-else expressions
9. Match expressions

### Functions & Data (11 features)

10. For loops
11. While loops
12. Loop control (break, continue)
13. Function definitions
14. Function parameters and returns
15. Closures and lambdas
16. Higher-order functions
17. Arrays
18. Tuples
19. Objects/Maps
20. Structs

### Advanced (10 features)

21. Enums
22. Pattern destructuring
23. Pattern guards
24. Exhaustiveness checking
25. Try-catch error handling
26. Option type
27. Result type
28. String interpolation (f-strings)
29. String methods
30. String escaping

### Standard Library (10 features)

31. File I/O (fs)
32. HTTP client
33. JSON parsing
34. Path operations
35. Environment variables
36. Process execution
37. Time/Date operations
38. Logging
39. Regular expressions
40. DataFrames

### Meta (1 feature)

41. WASM compilation

## Let's Begin

Ready to see the proof? Let's start with the basics: literals.

Continue to Basic Syntax →