[erlang-questions] Bit syntax
Bob Cowdery
bob@REDACTED
Wed Mar 9 16:09:59 CET 2011
What I actually want is 51 bytes of 16#00.
12> <<A:24, B:48, C:408>> = <<16#effe02:24,16#00:48,16#00:408>>.
** exception error: no match of right hand side value
<<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,...>>
Why is this different. Isn't it just saying 00 as a 408 bit number
rather than (8*51)?
Bob
On 09/03/2011 14:55, Vlad Dumitrescu wrote:
> Your C is 8*51 as a 408 bit number. You probably want 16#00:408 instead.
>
> /Vlad
>
> On Wed, Mar 9, 2011 at 15:50, Bob Cowdery <bob@REDACTED
> <mailto:bob@REDACTED>> wrote:
>
> 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
> <bob@REDACTED <mailto:bob@REDACTED>
> > <mailto:bob@REDACTED
> <mailto:bob@REDACTED>>> 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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