Joining A List Of Binaries In Erlang

The binary module provides an easy way to split binaries using split/2,3, but what if you want to join a list of binaries back together?

-spec binary_join([binary()], binary()) -> binary().
binary_join([], _Sep) ->
 <<>>;
binary_join([Part], _Sep) ->
 Part;
binary_join(List, Sep) ->
 lists:foldr(fun (A, B) ->
 if
 bit_size(B) > 0 -> <<A/binary, Sep/binary, B/binary>>;
 true -> A
 end
 end, <<>>, List).

It works just like you would expect:

binary_join([<<"Hello">>, <<"World">>], <<", ">>) % => <<"Hello, World">>
binary_join([<<"Hello">>], <<"...">>) % => <<"Hello">>

Hope you find this useful!

#erlang

Written by Daniel Kempkens

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4 Responses

Add your response

johnhaugeland

why not binary:list_to_bin/1

over 1 year ago ·

nifoc

binary:list_to_bin/1 is just list_to_binary/1 ... I feel like I'm missing something here. How would list_to_binary/1 do the same thing?

over 1 year ago ·

alternative
https://coderwall.com/p/746dgg

over 1 year ago ·

binaryjoin([<<"a">>, <<"b">>, <<"1">>], <<".">>). % => <<"a.b.1">>
binaryjoin([<<"a">>, 1, <<"b">>], <<".">>). % => ** exception error: bad argument
binary_join([<<"a">>, <<"b">>, 1], <<".">>). % => <<"a.b">> !!!

over 1 year ago ·