#!/usr/bin/python
from __future__ import division


def bloom(bits, hashes, keys):
    one_bit_fullness = 1/bits
    all_hashes_emptiness = (1-one_bit_fullness)**hashes
    all_keys_emptiness = all_hashes_emptiness**keys
    all_keys_fullness = 1 - all_keys_emptiness
    false_positive_probability = all_keys_fullness**hashes
    return {"keys": keys,
            "hashes": hashes,
            "bits": bits,
            "all_keys_fullness": all_keys_fullness,
            "false_positive_probability": false_positive_probability,
            }

if __name__ == '__main__':
    for hashes in 1, 3:
        for keys in 1, 32, 128, 256:
            print(('%(keys)d keys indexed with %(hashes)d hashes'
                  + ' in %(bits)d bits: fullness %(all_keys_fullness)f,'
                  + ' false positives %(false_positive_probability)f')
                  % bloom(256, hashes, keys))