# objectionary/eo

EOLANG, an Experimental Pure Object-Oriented Programming Language Based on 𝜑-Calculus

Repository: https://github.com/objectionary/eo
Canonical: https://ross.abutalabs.com/products/eo
Homepage: https://www.eolang.org
Language: Java
License: MIT
License Family: permissive
Topics: eolang, java, language, programming-language, oop, object-oriented-language, object-oriented-programming, object-oriented
Last push: 2026-08-26T18:59:28+00:00

## Health v2 (maintenance only)
Score: 94/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 99, release rhythm 83, longevity 100
- inputs: {"age_days": 3586, "days_push": 7, "days_rel": 33, "gap_med": 4, "n_releases_24m": 70}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1415, forks 243 (observed 2026-08-28T04:04:39.824719+00:00)

## What it is
EO (EOLANG) is an experimental pure object-oriented programming language based on 𝜑-calculus, implemented in Java. It deliberately rejects classes, inheritance, mutability, NULL, static methods, and other constructs it considers anti-patterns in mainstream OOP.

## Use cases
- write programs in a purely object-oriented language
- experiment with phi-calculus based computation
- compile EO programs to JVM bytecode
- study elegant objects principles without classes or inheritance
- research immutability-first language design

## When to choose
- you want to explore or research pure OO language design
- you're experimenting with formal calculus-based programming models
- you want a JVM language with no classes, mutability, or NULL

## When to avoid
- you need a production-ready language with mature tooling
- you rely on classes, inheritance, or mutable state
- you need a large ecosystem and community libraries

## Facets
- artifact type: cli-tool
- maturity: active
- function: programming-language, compiler, interpreter
- domain: programming-languages, compilers, developer-tools
- platform: jvm, cross-platform
- tags: eolang, phi-calculus, object-oriented, experimental-language, elegant-objects, immutable, programming-language

## Member repositories
- objectionary/eo (main) score 94

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:04:39.824719+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T08:33:12.974355+00:00, confidence not recorded.
  - readme: https://github.com/objectionary/eo (fetched 2026-08-28T04:04:39.824719+00:00, sha 518f849097c8)
  - homepage: https://www.eolang.org (fetched 2026-08-29T11:50:54.791406+00:00, sha 98628cadd75a)
- Data as of 2026-08-30T08:39:29.467469+00:00.