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August 25, 2016 20:09
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Generates encode and decode methods for base 2->62
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for {base, name} <- (2..62 |> Enum.map(&({&1, "Base#{&1}" |> String.to_atom}))) do | |
# NOTE: Modules will be named :Base2, :Base3, ..., :Base62 | |
defmodule name do | |
@moduledoc """ | |
Automatically generated #{name} encode/decode functions | |
""" | |
@base base | |
@alphabet [?0..?9, ?a..?z, ?A..?Z] | |
|> Enum.flat_map(fn x -> x end) | |
|> to_string | |
|> String.split("", trim: true) | |
|> Enum.take(@base) | |
@validator Regex.compile!("^[#{ @alphabet |> Enum.join }]+$") | |
def alphabet, do: @alphabet |> Enum.join | |
for {char, ix} <- (@alphabet |> Enum.with_index) do | |
defp index_of(unquote(char)), do: unquote(ix) | |
defp char_at(unquote(ix)), do: unquote(char) | |
end | |
@doc """ | |
Encodes an integer to a #{name} string | |
## Examples | |
\tiex> :#{name}.encode(123) | |
""" | |
def encode(int) when is_integer(int) do | |
encode(div(int, @base), rem(int, @base), "") | |
end | |
defp encode(0, mod, str), do: char_at(mod) <> str | |
defp encode(int, mod, str) when is_integer(int) do | |
encode(div(int, @base), rem(int, @base), char_at(mod) <> str) | |
end | |
@doc """ | |
Decodes a #{name} string to an integer | |
## Examples | |
\tiex> :#{name}.decode("foo") | |
""" | |
def decode(str) when is_binary(str) do | |
case Regex.match?(@validator, str) do | |
false -> | |
{:error, "Not a valid #{unquote(name)} string"} | |
true -> | |
{:ok, str | |
|> String.reverse | |
|> String.split("", trim: true) | |
|> Enum.with_index | |
|> Enum.reduce(0, fn({char, index}, acc) -> acc + index_of(char) * (:math.pow(@base, index) |> round) end) | |
} | |
end | |
end | |
end | |
end |
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