Chamming distance is added

[Eldar7]

Due to recent request https://groups.google.com/forum/#!topic/annoy-user/FheMHkmgjpk chamming distance was added to available distances.

Chamming is a correct hamming distance:
chamming([a,b,c,d],[a,c,b,d]) = 2

[Eldar7]

ouch, it worked fine with f29296c commit.

[erikbern]

What's Chamming distance? Can you send a link to an explanation?

[Eldar7]

It is regular hamming distance https://en.m.wikipedia.org/wiki/Hamming_distance that can be applied to any vectors, not only to binary vectors.

Due to wiki:
The Hamming distance between:
"karolin" and "kathrin" is 3.

[erikbern]

Can you get this one to pass the tests?

[lbertolotti]

# -*- coding: utf-8 -*-
"""
Spyder Editor
"""
import annoy
import inspect

u = annoy.AnnoyIndex(5,metric='hamming')
u.add_item(0,'12346')
u.add_item(1,'12345')
u.build(1)
u.save('tree')
u.get_n_items()

In:u.get_distance(0,1)
Out: 0.0

[Eldar7]

@erikbern , ok, I'll try to make this one to pass the tests.