[erlang-questions] How to pass the length of binary to match into a function that matches the binary?

Ulf Wiger <>
Mon Nov 24 14:26:26 CET 2014


On 24 Nov 2014, at 13:56, Russell Brown <> wrote:

> Hi,
> Is there a way to do this:
> 
> my_fun(Bin, Len, <<Bin:Len/binary, Rest/binary>>) ->
> 	%% do stuff with Bin
> 	ok.
> 
> Len is unbound is the reason I can’t, but it seems like the sort of thing that would be useful if I could.

Yes, it’s slightly unfortunate, but you can write:

my_fun(B, Len, Binary) ->
    case Binary of
        <<B:Len/binary, Rest/binary>> ->
            %% do stuff with B
            ok;
        …
    end.

BR,
Ulf W

Ulf Wiger, Co-founder & Developer Advocate, Feuerlabs Inc.
http://feuerlabs.com



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