[erlang-questions] Missing binary BIFs

Loïc Hoguin <>
Thu Feb 9 12:51:35 CET 2012


Hm I would be very surprised if binary_to_list(list_to_binary(L)) /= L 
wouldn't be true. Do you have an example of this?

On 02/09/2012 12:48 PM, Robert Raschke wrote:
> Sure, but don't you usually use them in pairs? Just wondering cause
> list_to_binary/1 and binary_to_list/1 are not opposites of each other,
> that is, binary_to_list(list_to_binary(L)) /= L in general. But I'm
> guessing that probably doesn't matter for your use case.
>
> On Thu, Feb 9, 2012 at 11:31 AM, Loïc Hoguin <
> <mailto:>> wrote:
>
>     Those encode the term in the Erlang term format, which has a very
>     particular purpose. The functions I'm talking about are just
>     conversion from one type to binary strings.
>
>
>     On 02/09/2012 12:29 PM, Robert Raschke wrote:
>
>         Are you guys sure you're not looking for term_to_binary/1 and
>         binary_to_term/1 ?
>
>         On Thu, Feb 9, 2012 at 10:27 AM, Loďc Hoguin <
>         <mailto:>
>         <mailto: <mailto:>>> wrote:
>
>             While seemingly practical, I'm not sure why I would want any
>         place
>             in my code where I wouldn't be sure what the input type is. Even
>             with dialyzer checks I'm sure I would make false assumptions
>         and get
>             surprises here and there.
>
>             I also would like an efficient solution, both in processing
>         speed
>             and memory use. Converting to list then binary isn't that great,
>             even less so after module:function calls with guards.
>
>
>             On 02/09/2012 09:03 AM, Rapsey wrote:
>
>                 I wrote functions that convert between all types that I use
>                 constantly.
>                 Much easier to just force a specific type somewhere if
>         you're
>                 not sure
>                 what the input type is going to be instead of doing checks
>                 everywhere or
>                 annoying conversions like the one you wrote.
>                 It has a dependency on mochinum:digits/1 though.
>
>                 tolist(<<_/binary>> = P) ->
>                 binary_to_list(P);
>                 tolist(P) when is_atom(P) ->
>                 atom_to_list(P);
>                 tolist(P) when is_integer(P) ->
>                 integer_to_list(P);
>                 tolist(P) when is_float(P) ->
>                 mochinum:digits(P);
>                 tolist(P) when is_list(P) ->
>                 P.
>
>                 tobin(<<_/binary>> = P) ->
>                 P;
>                 tobin(P) when is_list(P) ->
>                 iolist_to_binary(P);
>                 tobin(P) when is_atom(P) ->
>                 atom_to_binary(P,latin1);
>                 tobin(P) when is_integer(P) ->
>                 tobin(integer_to_list(P));
>                 tobin(P) when is_float(P) ->
>                 tobin(mochinum:digits(P)).
>
>                 toatom(P) when is_binary(P) ->
>                 binary_to_atom(P,latin1);
>                 toatom(P) when is_list(P) ->
>                 list_to_atom(P);
>                 toatom(P) when is_atom(P) ->
>                 P.
>                 toint(<<_/binary>> = P) ->
>                 list_to_integer(binary_to_____list(P));
>
>                 toint([_|_] = P) ->
>                 list_to_integer(P);
>                 toint(P) when is_integer(P) ->
>                 P;
>                 toint(P) when is_float(P) ->
>                 erlang:round(P).
>                 tofloat(P) when is_integer(P) ->
>                 P / 1;
>                 tofloat(P) when is_float(P) ->
>                 P;
>                 tofloat(P) when is_binary(P) ->
>                 tofloat(binary_to_list(P));
>                 tofloat(P) when is_list(P) ->
>                 Str = string:join(string:tokens(P,",____"),"."),
>
>                 case string:str(Str,".") of
>                 0 ->
>                 tofloat(P ++ ".0");
>                 _ ->
>                 list_to_float(Str)
>                 end;
>                 tofloat(P) ->
>                 list_to_float(tolist(P)).
>
>
>                 On Wed, Feb 8, 2012 at 7:29 PM, Loďc Hoguin
>         < <mailto:>
>         <mailto: <mailto:>>
>
>         <mailto: <mailto:>
>         <mailto: <mailto:>>>> wrote:
>
>                     Hello,
>
>                     It feels a bit tedious to keep doing things like
>                       list_to_binary(integer_to_______list(42))
>
>                     or even
>                       list_to_binary(atom_to_list(______forty_two))
>
>
>
>                     when we could have convenient integer_to_binary/1 or
>         /2 or
>                     atom_to_list/1 BIFs.
>
>                     Is there any chance to add them in a future release?
>         With
>                 all the
>                     advantages of binaries it's a shame it's not easier
>         to deal
>                 with them.
>
>                     Thanks.
>
>                     --
>                     Loďc Hoguin
>                     Erlang Cowboy
>                     Nine Nines
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>
>             Erlang Cowboy
>             Nine Nines
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-- 
Loïc Hoguin
Erlang Cowboy
Nine Nines



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