unification 0.2.1

Unification

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.

History

This was carved out from the LogPy and Multiple Dispatch projects.

Author

Matthew Rocklin