eopsin-lang 0.2.1

A simple pythonic programming language for Smart Contracts on Cardano

Eopsin

This is a prototypical implementation of smart contracts for Cardano which are written in a very strict subset of valid Python. The general philosophy of this project is to write a compiler that ensure the following:

If the program compiles then:

1. it is a valid Python program
2. the output running it with python is the same as running it on-chain.

This means that not every valid python program is a valid smart contract. Not all language features of python will or can be supported. The reasons are mainly of practical nature (i.e. we can't infer types when functions like eval are allowed). Specifically, only a pure subset of python is allowed. Further, only immutable objects may be generated.

For your program to be accepted, make sure to only make use of language constructs supported by the compiler. You will be notified of which constructs are not supported when trying to compile.

Smart Contracts

A simple contract called the "Cancel Contract" verifies that only specific wallets can withdraw money. They are authenticated by a signature.

from eopsin.prelude import *


class CancelDatum(PlutusData):
    pubkeyhash: bytes


def validator(datum: CancelDatum, redeemer: None, context: ScriptContext) -> bool:
    res = False
    for s in context.tx_info.signatories:
        if datum.pubkeyhash == s.value:
            res = True
    return res

All contracts written in eopsin are 100% valid python. See the examples directory for more.

Installation

Install Python 3.10. Then run

python3 -m pip install eopsin-lang

Running

Write your program in python. You may start with the content of examples. Arguments to scripts are passed in as Plutus Data objects in JSON notation.

You can run any of the following commands

# Evaluate script in Python
python3 -m eopsin eval examples/sum_sc.py "{\"int\": 4}" "{\"int\": 38}" "{\"constructor\": 0, \"fields\": []}"

# Compile script to 'uplc', the Cardano Smart Contract assembly
python3 -m eopsin compile examples/sum_sc.py

# Compile script to 'uplc', and evaluate the script in UPLC (for debugging purposes)
python3 -m eopsin eval_uplc examples/sum_sc.py "{\"int\": 4}" "{\"int\": 38}" "{\"constructor\": 0, \"fields\": []}"

# Compile script to 'pluto', an intermediate language (for debugging purposes)
python3 -m eopsin compile_pluto examples/sum_sc.py

Name

Eopsin (Korean: 업신; Hanja: 業神) is the goddess of the storage and wealth in Korean mythology and shamanism. [...] Eopsin was believed to be a pitch-black snake that had ears. [1]

Since this project tries to merge Python (a large serpent) and Pluto/Plutus (Greek wealth gods), the name appears fitting.

Contributing

Architecture

This program consists of a few independent components:

1. An aggressive static type inferencer
2. Rewriting tools to simplify complex python expressions
3. A compiler from a subset of python into UPLC

Sponsoring

You can sponsor the development of eopsin. Just drop me a message on social media and let me know what it is for.