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Contents
defmodule ISBNVerifier do
@doc """
Checks if a string is a valid ISBN-10 identifier
## Examples
iex> ISBNVerifier.isbn?("3-598-21507-X")
true
iex> ISBNVerifier.isbn?("3-598-2K507-0")
false
"""
@spec isbn?(String.t()) :: boolean
def isbn?(isbn) do
if Regex.match?(~r/^(\d-?){9}(\d|X)$/, isbn) do
checksum =
isbn
|> String.replace("-", "")
|> String.graphemes()
|> Enum.zip(10..1)
|> Enum.map(&checksum_weighting/1)
|> Enum.sum()
rem(checksum, 11) == 0
else
false
end
end
defp checksum_weighting({"X", 1}), do: 10
defp checksum_weighting({digit, weight}) do
String.to_integer(digit) * weight
end
end
Version data entries
52 entries across 52 versions & 1 rubygems