sum-walker 0.6.4

PURPOSE

The sum_walker PyPI distribution allows one to iterate over increasing sums of a certain number (e.g: 2 or 3) of elements out of a stream of increasing integers.

INSTALLATION

pip3 install sum_walker

USAGE

A simple example of printing sums of two integers:

#! /usr/bin/env python3
# -*- coding: utf-8 -*-
# vim:fenc=utf-8
#
# Copyright © 2020 Shlomi Fish <shlomif@cpan.org>
#
# Distributed under the terms of the MIT license.
#
# This program displays increasing sums of two positive integers

from six import print_

from sum_walker import DWIM_SumWalker


def main():
    seq = [1, 2, 3, 4]

    def request_more():
        nonlocal seq
        seq.append(seq[-1] + 1)

    it = DWIM_SumWalker(2, seq, request_more)

    def print_next():
        nonlocal it
        sum_, coords = next(it)
        print_("{} = {}".format(
            sum_, " ; ".join(
                [" + ".join([str(seq[x]) for x in permutation])
                 for permutation in coords])))

    # Prints «2 = 1 + 1»
    print_next()

    # Prints «3 = 1 + 2»
    print_next()

    # Prints «4 = 1 + 3 ; 2 + 2»
    print_next()

    # Prints «5 = 1 + 4 ; 2 + 3»
    print_next()

    # Prints «6 = 1 + 5 ; 2 + 4 ; 3 + 3»
    print_next()


main()

A more interesting example:

# Finding sums of two powers of 3 (= i**3 ) in two or more
# different ways:
#
# https://en.wikipedia.org/wiki/Taxicab_number
from sum_walker import DWIM_SumWalker

seq = [0, 1]
reached = 2

def request_more():
    nonlocal reached
    nonlocal seq
    seq.append(reached ** 3)
    reached += 1

it = DWIM_SumWalker(2, seq, request_more)
for sum_, coords in it:
    len_ = len(coords)
    if len_ > 1:
        print("{}\t{}\t{}".format(
            len_, sum_, " ; ".join(
                [" + ".join(["{} ** 3".format(x) for x in c])
                 for c in coords])))

NOTES

COPYRIGHT

Copyright © 2020, Shlomi Fish. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions, and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions, and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the author of this software nor the names of contributors to this software may be used to endorse or promote products derived from this software without specific prior written consent.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.