Skip to content

Straightforward unification in Python that's extensible via generic functions.

License

Notifications You must be signed in to change notification settings

pythological/unification

 
 

Repository files navigation

Unification

Build Status Coverage

Straightforward Unification, extensible via dispatch.

Examples

>>> from unification import *
>>> unify(1, 1)
{}
>>> unify(1, 2)
False
>>> x = var('x')

>>> unify((1, x), (1, 2))
{~x: 2}

>>> unify((x, x), (1, 2))
False

@unifiable
class Account(object):
    def __init__(self, id, name, balance):
        self.id = id
        self.name = name
        self.balance = balance

data = [Account(1, 'Alice', 100),
        Account(2, 'Bob', 0),
        Account(2, 'Charlie', 0),
        Account(2, 'Denis', 400),
        Account(2, 'Edith', 500)]

id, name, balance = var('id'), var('name'), var('balance')

>>> [unify(Account(id, name, balance), acct) for acct in data]
[{~name: 'Alice', ~balance: 100, ~id: 1},
 {~name: 'Bob', ~balance: 0, ~id: 2},
 {~name: 'Charlie', ~balance: 0, ~id: 2},
 {~name: 'Denis', ~balance: 400, ~id: 2},
 {~name: 'Edith', ~balance: 500, ~id: 2}]

>>> [unify(Account(id, name, 0), acct) for acct in data]
[False,
 {~name: 'Bob', ~id: 2},
 {~name: 'Charlie', ~id: 2},
 False,
 False]

Function Dispatch

Unification supports function dispatch through pattern matching.

from unification.match import *

n = var('n')
@match(0)
def fib(n):
    return 0

@match(1)
def fib(n):
    return 1

@match(n)
def fib(n):
    return fib(n - 1) + fib(n - 2)

>>> map(fib, [0, 1, 2, 3, 4, 5, 6, 7, 8, 0])
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

This patten matching can be fairly complex

name, amount = var('name'), var('amount')

@match({'status': 200, 'data': {'name': name, 'credit': amount}})
def respond(name, amount):
    balance[name] +=  amount


@match({'status': 200, 'data': {'name': name, 'debit': amount}})
def respond(name, amount):
    balance[name] -= amount


@match({'status': 404})
def respond():
    print("Bad Request")

See full example in the examples directory.

Performance and Reliability

This was hacked together. Unification stresses extensibility over performance, preliminary benchmarks show that this is 2-5x slower than straight tuple-based unification.

This is somewhat reliable, the only caveat is on set unification which is challenging to do generally within this framework. It should work well in moderately complex cases but break down under very complex ones.

History

This project is a fork of unification.

About

Straightforward unification in Python that's extensible via generic functions.

Topics

Resources

License

Stars

Watchers

Forks

Sponsor this project

 

Packages

No packages published

Contributors 7