Elixir range utilities: constant-time random sampling and set operations.

First, please make sure that you’re running Erlang/OTP 18.0 or newer.

Add range_extras to your list of dependencies in mix.exs:

def deps do
  [{:range_extras, "~> 0.1.0"}]
end

Run mix deps.get.

Read the latest documentation at https://hexdocs.pm/range_extras/.

• union/2
• difference/2
• intersection/2

These functions take two ranges and return a list of zero to two ranges:

iex> RangeExtras.union(1..4, 3..5)
[1..5]
iex> RangeExtras.difference(8..1, 4..4)
[8..5, 3..1]
iex> RangeExtras.intersection(8..1, -4..0)
[]

They’re implemented as simple cond clauses that match on the start and end values of the ranges, so they run in constant time.

Ranges are always inclusive.

The direction of the resulting ranges is the same as the direction of the first given range:

iex> RangeExtras.union(1..4, 3..5)
[1..5]
iex> RangeExtras.union(4..1, 3..5)
[5..1]

• random/1

Works in the same way as Enum.random/1, but runs in constant time as well since it only uses the start and end values of the range.

The implementation uses Erlang’s :rand module. You don’t need to seed the generator like you have to currently do with Enum.random/1 that uses :random instead.

(The development version of Elixir now uses :rand.)

ISC License (ISC)

Copyright © 2015 Leo Nikkilä

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

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