[erlang-questions] binary elements greater than 255

Valentin Micic <>
Sat Apr 26 08:40:02 CEST 2008


Well... is it only shell? Say I write a function like:

F=fun(A) -> <<0, A>> end.

and then do:

> F( 10 ).
> <<0, 10>>
...
> F(100).
> <<0, 100>>
...
> F(1000).
> <<0, 232>>
...
> F(10000000).
> <<0, 128>>
...
> F(1111111111).
> <<0, 199>>

I've been under impression that functional objects are implicitly compiled, 
therefore behave like any ERLANG program, thus, should generate exception 
for, say,  F(1000). I suppose, one should not assume anything, eh?

V.

PS
This does not seem to be a new thing, as I can trace the same behaviour back 
to R9C.


----- Original Message ----- 
From: "Peter Lund" <>
To: "Igor Ribeiro Sucupira" <>
Cc: <>; "Zvi" <>
Sent: Saturday, April 26, 2008 7:04 AM
Subject: Re: [erlang-questions] binary elements greater than 255


> Please observe that this is just how the shell works...
>
> In any erlang program you make, you would use the list_to_binary/1 
> function.
>
> Eshell V5.3  (abort with ^G)
> 1> <<0,1111111111>>.
> <<0,199>>
> 2> list_to_binary([0,1111111111]).
>
> =ERROR REPORT==== 26-Apr-2008::07:02:13 ===
> Error in process <0.24.0> with exit value:
> {badarg,[{erlang,list_to_binary,[[0,16#423A35C7]]},{erl_eval,do_apply1,5},{shell,eval_loop,2}]}
>
> ** exited: {badarg,[{erlang,list_to_binary,[[0,1111111111]]},
>                    {erl_eval,do_apply1,5},
>                    {shell,eval_loop,2}]} **
>
> And here you get a proper crash
>
> With correct indata you get good output.
>
> 3> list_to_binary([0,111,255]).
> <<0,111,255>>
>
> /Peter
>
>
> Igor Ribeiro Sucupira skrev:
>> I think this is the classic situation "If you do it wrong, the
>> behaviour is undefined".  :-)
>> (On the case at hand, it looks it's just taking the least significant
>> byte from the number)
>>
>> In fact, maybe it should raise a warning when compiling a module with
>> this kind of code... (?)
>>
>> On Fri, Apr 25, 2008 at 10:01 PM, Zvi <> wrote:
>>
>>>  Hi Igor,
>>>
>>>  I know that lately computer industry decided to switch from 6-bit to 
>>> 8-bit
>>>  bytes :), which when unsigned can hold values in range 0..255. But this
>>>  wasn't my question. I asked, why Erlang compiler didn't return error, 
>>> when
>>>  you give it input like <<256>>. I think it's a bug.
>>>
>>>  Zvi
>>>
>>>
>>>  Igor Ribeiro Sucupira wrote:
>>>  >
>>>  > No.
>>>  > If you use integers in a binary, each must be in the range [0, 255]
>>>  > (1-byte).
>>>  >
>>>  > Igor.
>>>  >
>>>  > On Fri, Apr 25, 2008 at 7:44 PM, Zvi <> wrote:
>>>  >>
>>>  >>  Is this a bug?
>>>  >>  Zvi
>>>  >>  ------------------------------------------------------------
>>>  >>  Erlang (BEAM) emulator version 5.6 [smp:2] [async-threads:0]
>>>  >>
>>>  >>  Eshell V5.6  (abort with ^G)
>>>  >>  1>
>>>  >>  1> <<0,255>>.
>>>  >>  <<0,255>>
>>>  >>  2> <<0,256>>.
>>>  >>  <<0,0>>
>>>  >>  3> <<0,257>>.
>>>  >>  <<0,1>>
>>>  >>  4> <<0,65536>>.
>>>  >>  <<0,0>>
>>>  >>  5> <<0,1111111111>>.
>>>  >>  <<0,199>>
>>>  >>  6>
>>>
>> _______________________________________________
>> erlang-questions mailing list
>> 
>> http://www.erlang.org/mailman/listinfo/erlang-questions
>>
>>
>
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