[erlang-questions] erlang's binary representation of 7 compared to other languages

Woody Peterson <>
Fri Jul 30 03:51:40 CEST 2010


Thanks for the quick reply! So you're saying erlang can't be made to  
recognize "\a"; any idea why "\07" and "\a" are considered equivalent,  
but the two languages chose incompatible representations? Or, if  
erlang can't parse "\a" (I was hoping for an option a la http://www.erlang.org/doc/programming_examples/bit_syntax.html#id2261157) 
, I guess the simplest answer is how to get ruby to output "\07",  
which isn't on topic here.

I'm always down for a quick fix, so I'll see if any rubyists know how  
to accomplish the latter, but I'm going to lose sleep if I don't know  
why the opposing designs exist in the first place :)

On Jul 29, 2010, at 6:36 PM, Michael Truog wrote:

> I think this is just because Erlang does not recognize the "\a"  
> encoding
> and instead just recognizes "a" ("\07" seems best in this case, and is
> equivalent to "\a"):
> 4> <<"\n">>.
> <<"\n">>
> 5> <<"\a">>.
> <<"a">>
> 6> <<"\07">>.
> <<7>>
> 7>
>
> - Michael
>
> On 07/29/2010 06:19 PM, Woody Peterson wrote:
>> I have a problem that's on the borders of ruby and erlang, and I
>> figured the erlang list would generally be more familiar with binary
>> issues. And forgive me for my haziness with the terminology here...
>>
>> The basic problem is that ruby encodes the integer 7 as "\a", while
>> erlang only decodes it as "\007". Ruby *will* decode both "\007" and
>> "\a" into 7, which makes me think there's more than one opinion about
>> how it should be encoded.
>>
>> The bigger problem is I'm trying to send data from ruby to erlang via
>> BERT, and turns out it can't handle data (broadly defined) of  
>> length 7.
>>
>> Here's some code examples:
>>
>> ruby:
>>
>>    [7].pack("C") # => "\a"
>>    "\a".unpack("C") # => 7
>>    "\007".unpack("C") # => 7
>>
>> erlang:
>>
>>    <<"\a">>. % => <<a>>
>>    <<"\007">>. % => <<7>>
>>
>> That's all I've got. Not sure exactly what to google here, "erlang OR
>> ruby binary 007" doesn't really get me anywhere (suprise!), plus I'm
>> not sure what exactly this encoding/decoding specification is called.
>>
>> Any help is appreciated, even google terms :p
>>
>> -Woody
>>
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