[erlang-questions] Bit syntax

Bob Cowdery <>
Wed Mar 9 15:50:46 CET 2011


Thanks. The syntax did look a bit odd for a repeating group. I pulled it
off the web somewhere.

So if I say:

7> <<A:24, B:48, C:408>> = <<16#effe02:24,16#00:48,(8*51):408>>
.
<<239,254,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
  0,0,0,...>>
8> A.
15728130
9> B.
0
10> C.
408

What do these bound values mean. C is supposed to be 51 zero bytes (408
bits). Why is C bound to the number of bits.

Bob

On 09/03/2011 14:29, Vlad Dumitrescu wrote:
> Hi!
>
> On Wed, Mar 9, 2011 at 15:21, Bob Cowdery <
> <mailto:>> wrote:
>
>     Hi
>
>     I'm clearly not understanding the bit syntax properly. Could someone
>     explain to me what I am doing wrong here. Why does the first not match
>     when its the right shape but the second does when its the wrong shape.
>     The bound values don't make much sense to me either.
>
>     1> <<A:24, B:48, C:408>> = <<16#effe02:24,16#00:48,16#00,(8*51):408>>.
>     ** exception error: no match of right hand side value
>
>
> There is an "extra" 16#00 on the right side that is not matched on the
> left.
>  
>
>     2> <<A:32, B:48, C:408>> = <<16#effe02:24,16#00:48,16#00,(8*51):408>>.
>
>
> The larger size for A "swallows" the extra value, but shifts the
> values a byte to the right.
>
> regards,
> Vlad
>



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