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fast

0.11.0
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A grab bag of utilities I tend to want, so I can build faster.

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fast lib guards.ex
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lib/guards.ex 

defmodule Fast.Guards do

  defguard is_uuid4(s)

           # hyphens at 8, 13, 18, 23

           # version nibble '4' at pos 14

           # variant nibble 8|9|a|b (case-insensitive) at pos 19

           when is_binary(s) and byte_size(s) == 36 and

                  binary_part(s, 8, 1) == "-" and

                  binary_part(s, 13, 1) == "-" and

                  binary_part(s, 18, 1) == "-" and

                  binary_part(s, 23, 1) == "-" and

                  binary_part(s, 14, 1) == "4" and

                  (binary_part(s, 19, 1) == "8" or

                     binary_part(s, 19, 1) == "9" or

                     binary_part(s, 19, 1) == "a" or

                     binary_part(s, 19, 1) == "A" or

                     binary_part(s, 19, 1) == "b" or

                     binary_part(s, 19, 1) == "B")

end