Error-Lang Playground

A teaching playground for Error-Lang — the programming language where code breaks intentionally.

Overview

Error-Lang Playground provides a structured learning environment for Error-Lang, a teaching-first language designed to teach how compilers and interpreters work by making errors the curriculum.

Philosophy

Errors are features, not bugs. Every error has a lesson.

Traditional programming focuses on avoiding errors. Error-Lang embraces them:

• Intentional error injection in designated "gutter" blocks

• Stability score that decreases with each error

• Curriculum-mapped error codes (E0001-E0010+)

• Error-tolerant parsing that continues after failures

Quick Start

# Clone the playground
git clone https://github.com/hyperpolymath/error-lang-playground
cd error-lang-playground

# Setup (install ReScript)
just setup

# Build
just build

# Run your first level
just run-hello

# Or run any level
just run levels/02-smart-quotes.err

# Learn about an error code
just explain E0007

Levels

The playground includes progressive learning levels:

Level	Topic	Error Codes
01	Hello World	(none)
02	Smart Quotes	E0007
03	Unterminated Strings	E0002
04	Escape Sequences	E0003
05	Missing Block Terminators	E0005
06	Unmatched Parentheses	E0006
07	Illegal Characters	E0004
08	Variables and Types	(none)
09	Operators	(none)
10	Gutter Mastery	(all)

Run just levels to see all available levels.

Error Codes

Syntax Errors (E0001-E0010)

Code	Description
E0001	Unexpected token
E0002	Unterminated string literal
E0003	Invalid escape sequence
E0004	Illegal character
E0005	Missing 'end' keyword
E0006	Unmatched parenthesis
E0007	Smart quote detected
E0008	Invalid identifier
E0009	Reserved keyword misuse
E0010	Whitespace issue

Use just explain <code> for detailed explanations.

The Gutter Block

The gutter block is Error-Lang’s signature feature:

main
    println("This always works")

    gutter
        # Errors may be injected here
        let broken = "unterminated
    end

    println("This still runs!")
end

How It Works

1. Code inside gutter…​end is an "error zone"

2. The compiler may inject random errors (based on seed)

3. Each error decreases the Stability Score

4. The compiler recovers and continues after end

Stability Score

Score	Status
100%	Rock solid
70%+	Stable
50%+	Wobbly
30%+	Unstable
<10%	Critical
0%	Collapsed

Project Structure

error-lang-playground/
├── compiler/
│   └── src/
│       ├── lexer/       # Tokenization
│       ├── parser/      # Syntax analysis
│       ├── types/       # Type definitions
│       └── errors/      # Error injection system
├── cli/
│   └── main.js          # Deno CLI entry point
├── levels/              # Learning levels (*.err)
├── examples/            # Additional examples
├── docs/                # Documentation
├── tests/               # Test suite
├── rescript.json        # ReScript config
├── deno.json            # Deno config
└── justfile             # Task runner

CLI Commands

# Run a program
error-lang run <file.err>

# Explain an error code
error-lang explain E0002

# List levels
error-lang levels

# Check environment
error-lang doctor

# Show help
error-lang help

Development

Prerequisites

• Deno 1.40+

• Node.js 18+ (for ReScript compiler)

• just (task runner)

Building

just build        # Build everything
just build-watch  # Watch mode
just clean        # Remove artifacts

Testing

just test         # Run tests
just test-watch   # Watch mode
just check        # Full lint/format/type check

Technology Stack

• Compiler: ReScript (compiles to JavaScript)

• CLI: Deno (TypeScript-free, Node-free runtime)

• Documentation: AsciiDoc

• Task Runner: just

This follows the Rhodium Standard Repositories language policy.

Related Projects

• error-lang - The Error-Lang language specification and core implementation

License

PMPL-1.0-or-later

Contributing

See CONTRIBUTING.adoc for guidelines.