Rune-stone

Multi-Language Example: One Spec, Two Languages

This example demonstrates RUNE’s language-agnostic nature. A single .rune spec produces consistent implementations in different languages.

The Spec

slugify.rune defines a function that converts text into URL-friendly slugs. The spec uses language: any and a language-neutral signature:

function slugify(text: string, separator: string = "-") -> string

The behavior, constraints, edge cases, and tests are the same regardless of target language.

The Implementations

Python

# python/slugify.py
def slugify(text: str, separator: str = "-") -> str:
    normalized = unicodedata.normalize("NFKD", text)
    ascii_text = normalized.encode("ascii", "ignore").decode("ascii")
    slug = re.sub(r"[^a-z0-9\s-]", "", ascii_text.lower())
    ...

Uses unicodedata.normalize() from the standard library for accent removal.

TypeScript

// typescript/slugify.ts
export function slugify(text: string, separator: string = "-"): string {
    let slug = text.split("").map(c => ACCENT_MAP[c] ?? c).join("");
    slug = slug.toLowerCase().replace(/[^a-z0-9\s-]/g, "");
    ...

Uses a character map for accent replacement (no native NFKD in browser JS).

Same Tests, Same Results

Both implementations pass the exact same test cases from the spec:

Test	Python	TypeScript
slugify("Hello World")	"hello-world"	"hello-world"
slugify("Café Résumé")	"cafe-resume"	"cafe-resume"
slugify(" too many spaces ")	"too-many-spaces"	"too-many-spaces"
slugify("Hello World", "_")	"hello_world"	"hello_world"

Different languages, different idioms, same behavior. That’s the point.

Running the Tests

Python:

cd examples/multi-language/python
pip install pytest
pytest test_slugify.py -v

TypeScript:

cd examples/multi-language/typescript
npm install --save-dev typescript jest ts-jest @types/jest
npx jest slugify.test.ts

Directory Structure

multi-language/
├── README.md               # This file
├── slugify.rune            # Language-agnostic spec
├── python/
│   ├── slugify.py          # Python implementation
│   └── test_slugify.py     # Python tests (pytest)
└── typescript/
    ├── slugify.ts          # TypeScript implementation
    └── slugify.test.ts     # TypeScript tests (Jest)

Key Takeaway

The .rune spec defines what the function does. Each language decides how:

• Python uses unicodedata for Unicode normalization
• TypeScript uses a character map for accent replacement
• Both produce identical output for identical input

The spec is the contract. The implementation is the language’s job.

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