starter trying to figure out a binary pattern match

[Felipe Vieira]

Thanks for all of the answers (cheatsheet + pointers to resources). For
completeness the best I could come up with is:

```
-define(ID3V1_HEADER, "TAG").
⋯
is_id3v1(<<?ID3V1_HEADER, Tag:(128 -
byte_size(<<?ID3V1_HEADER>>))/binary>>) ->
⋯
```

‫‪Markus Greim‬‏ <‪greim@REDACTED‬‏> در تاریخ پنجشنبه ۲۱ اکتبر ۲۰۲۱
ساعت ۷:۰۰ نوشت:‬

> Hi Magnus,
>
> congratulations! this "cheat sheet" is fantastic, best explanation of
> Erlang binaries ever seen!
>
> <<"Grüße"/utf8>>
>
> Markus
> [image: Sent from Front]
>
> On October 21, 2021, 11:01 AM GMT+2 magnus.falk@REDACTED wrote:
>
> I made a cheat sheet for binaries that you may find useful:
> https://cheatography.com/fylke/cheat-sheets/erlang-binaries/
>
> Improvement suggestions welcome!
>
> Regards,
> Magnus
>
> On Thu, Oct 21, 2021 at 9:21 AM Nalin Ranjan <ranjanified@REDACTED>
> wrote:
>
>> If you prefer chatting, there is a link to get a slack
>> <https://erlef.org/slack-invite/erlanger> invitation under the community
>> <https://www.erlang.org/community> section of erlang.org.
>>
>> 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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