starter trying to figure out a binary pattern match

[Nalin Ranjan]

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Thanks and Regards
Nalin Ranjan

On Thu, Oct 21, 2021 at 9:37 AM Felipe Vieira <fmv1992@REDACTED> wrote:

> Hey folks, I have just started learning Erlang and I'm loving it.
>
> I'm going through Armstrong's "Programming Erlang" and I'm trying to build
> on "Reading MP3 Metadata".
>
> He patter matches with:
>
> ```
> parse_v1_tag(<<$T,$A,$G, Title:30/binary, Artist:30/binary, ⋯
> ```
>
> I tried the following (and variations):
>
> 1.
>
> ```
> -define(ID3V2_HEADER, "TAG").
> ⋯
> is_id3v2(<<?ID3V2_HEADER, Tag:(128 - byte_size(?ID3V2_HEADER))/binary>>) ->
> ```
>
> 2.
>
> ```
> -define(ID3V2_HEADER, <<"TAG":3/binary>>).
> ⋯
> is_id3v2(<<?ID3V2_HEADER, Tag:(128 - byte_size(?ID3V2_HEADER))/binary>>) ->
> ```
>
> And I'm trying to achieve a match like this (which also does not work, but
> states more clearly my intentions):
>
> ```
> <<"TAG">> ++ <<X>> = <<84,65,71,73,86,46,32,87,46>>.
> ```
>
> Is there a way to achieve this together with the `128 -
> byte_size(?ID3V2_HEADER))/binary>>` calculation?
>
> Best,
>
> PS: is there a more informal/chat-like place to ask these kinds of
> questions?
>
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