IO.puts generates ArgumentError on binary

[bmitc]

Hello! I am having an issue where IO.puts on a specific binary is generating an ArgumentError.

iex> IO.puts <<32, 32, 145, 225, 8, 179, 180, 12, 65, 83, 232, 51, 96, 25, 206, 113, 158, 163, 89, 233, 199, 129, 103, 78, 161, 83, 246, 125, 32, 250, 166, 202>>
** (ArgumentError) argument error
    (stdlib 3.16.1) io.erl:99: :io.put_chars(:standard_io, [<<32, 32, 145, 225, 8, 179, 180, 12, 65, 83, 232, 51, 96, 25, 206, 113, 158, 163, 89, 233, 199, 129, 103, 78, 161, 83, 246, 125, 32, 250, 166, 202>>, 10])
iex>

I am posting this in hopes of clarifying and checking my understanding, as I think I now understand why this is happening but am not 100% sure.

My understanding is that in Elixir, values of type String.t() are UTF-8 strings and are also of type binary(), but not necessarily the other way around in that all binary() are not String.t(). For example, you can have a binary which doesn’t represent a UTF-8 string. In Elixir, if a binary value represents a UTF-8 string, it is displayed as so, such as <<75, 90>> being displayed as "KZ".

The input type of IO.puts is chardata | String.Chars.t().

Is the ArgumentError above because the binary data doesn’t represent a UTF-8 string? Is encoding the binary to UTF-16 using Base.encode16/1 a way to always display binaries as string data? What’s the general way one should “print” binary data in Elixir?

Is this right or is there something else going wrong?

[benwilson512]

@bmitc

Is the ArgumentError above because the binary data doesn’t represent a UTF-8 string?

Yes.

@bmitc

Is encoding the binary to UTF-16 using Base.encode16/1 a way to always display binaries as string data?

That isn’t what Base.encode16 does. Base.encode16 encodes a binary as a hexadecimal utf8 string. It will however always return a printable string, no matter what binary you give it.

[bmitc]

@benwilson512

@bmitc

Is encoding the binary to UTF-16 using Base.encode16/1 a way to always display binaries as string data?

That isn’t what Base.encode16 does. Base.encode16 encodes a binary as a hexadecimal utf8 string. It will however always return a printable string, no matter what binary you give it.

Yea, that’s what I meant. My wording may have been off a bit. I meant to just use Base.encode16/1 as a way to convert any binary to a hexadecimal string.

Thank you for taking a look and confirming this! This was one of those situations where I got confused, typed up a draft, but then did more reading and sort of figured it out, but I wanted a gut check by posting here. Thanks again.