About "set bits"

About "set bits"

[Xue Fuqiao]

In (info "(elisp) Bindat Spec"):

  `bits LEN'
     List of set bits in LEN bytes.  The bytes are taken in big endian
     order and the bits are numbered starting with `8 * LEN - 1' and
     ending with zero.  For example: `bits 2' unpacks `#x28' `#x1c' to
     `(2 3 4 11 13)' and `#x1c' `#x28' to `(3 5 10 11 12)'.

I don't know what "set bits" means here.  I have searched the archives,
and found two related threads:
http://lists.gnu.org/archive/html/help-gnu-emacs/2005-06/msg00087.html
http://lists.gnu.org/archive/html/help-gnu-emacs/2013-01/msg00103.html

But they didn't help.  I have also searched the web and seen the
commentary header of bindat.el, but nothing helped to me.  Can I get a
pointer to information on this concept (or on byte packing)?

-- 
Xue Fuqiao

English is not my native language; please excuse typing errors.

Re: About "set bits"

[Thien-Thi Nguyen]

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() Xue Fuqiao <xfq.free@gmail.com>
() Wed, 10 Apr 2013 21:46:27 +0800

   I don't know what "set bits" means here.

See <http://foldoc.org/bit>, which defines "set"
(and "clear") with respect to a "bit".

M-x praise-foldoc RET

-- 
Thien-Thi Nguyen
GPG key: 4C807502

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Re: About "set bits"

[Eli Zaretskii]

> Date: Wed, 10 Apr 2013 21:46:27 +0800
> From: Xue Fuqiao <xfq.free@gmail.com>
> 
> In (info "(elisp) Bindat Spec"):
> 
>   `bits LEN'
>      List of set bits in LEN bytes.  The bytes are taken in big endian
>      order and the bits are numbered starting with `8 * LEN - 1' and
>      ending with zero.  For example: `bits 2' unpacks `#x28' `#x1c' to
>      `(2 3 4 11 13)' and `#x1c' `#x28' to `(3 5 10 11 12)'.
> 
> I don't know what "set bits" means here.

It means bits that are set, i.e. their value is 1.

Re: About "set bits"

[Barry Margolin]

In article <mailman.23883.1365607222.855.help-gnu-emacs@gnu.org>,
 Eli Zaretskii <eliz@gnu.org> wrote:

> > Date: Wed, 10 Apr 2013 21:46:27 +0800
> > From: Xue Fuqiao <xfq.free@gmail.com>
> > 
> > In (info "(elisp) Bindat Spec"):
> > 
> >   `bits LEN'
> >      List of set bits in LEN bytes.  The bytes are taken in big endian
> >      order and the bits are numbered starting with `8 * LEN - 1' and
> >      ending with zero.  For example: `bits 2' unpacks `#x28' `#x1c' to
> >      `(2 3 4 11 13)' and `#x1c' `#x28' to `(3 5 10 11 12)'.
> > 
> > I don't know what "set bits" means here.
> 
> It means bits that are set, i.e. their value is 1.

Xue's questions about documentation often seem to suggest that he 
doesn't know how to parse English. He frequently tries to interpret 
phrases as computer or Emacs jargon, when they just have the meaning the 
words imply.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: About "set bits"

[Xue Fuqiao]

On Wed, 10 Apr 2013 11:37:19 -0400
Barry Margolin <barmar@alum.mit.edu> wrote:

> In article <mailman.23883.1365607222.855.help-gnu-emacs@gnu.org>,
>  Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > > Date: Wed, 10 Apr 2013 21:46:27 +0800
> > > From: Xue Fuqiao <xfq.free@gmail.com>
> > > 
> > > In (info "(elisp) Bindat Spec"):
> > > 
> > >   `bits LEN'
> > >      List of set bits in LEN bytes.  The bytes are taken in big endian
> > >      order and the bits are numbered starting with `8 * LEN - 1' and
> > >      ending with zero.  For example: `bits 2' unpacks `#x28' `#x1c' to
> > >      `(2 3 4 11 13)' and `#x1c' `#x28' to `(3 5 10 11 12)'.
> > > 
> > > I don't know what "set bits" means here.
> > 
> > It means bits that are set, i.e. their value is 1.

I see, thanks.

> Xue's questions about documentation often seem to suggest that he 
> doesn't know how to parse English.  He frequently tries to interpret 
> phrases as computer or Emacs jargon, when they just have the meaning the 
> words imply.

I think you're right, and I'm trying to improve this problem.

-- 
Xue Fuqiao
http://www.gnu.org/software/emacs/

Re: About "set bits"

[Xue Fuqiao]

On Thu, 11 Apr 2013 06:33:28 +0800
Xue Fuqiao <xfq.free@gmail.com> wrote:

> > Xue's questions about documentation often seem to suggest that he 
> > doesn't know how to parse English.  He frequently tries to interpret 
> > phrases as computer or Emacs jargon, when they just have the meaning the 
> > words imply.
> 
> I think you're right, and I'm trying to improve this problem.
                                          ^^^^^^^
                                          resolve 
-- 
Xue Fuqiao
http://www.gnu.org/software/emacs/

Re: About "set bits"

[Thien-Thi Nguyen]

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() Barry Margolin <barmar@alum.mit.edu>
() Wed, 10 Apr 2013 11:37:19 -0400

   phrases as computer or Emacs jargon, when they just have the meaning
   the words imply.

Assuming that one can parse "set bit" as ADJ N, there is still room for
confusion.  Being around computers for a long time, i interpret "set" as
"having value 1", but recognize anyway that such is not universal.

For example, in the phrase "ready, set, go", the state "set" gives the
impression of suspense, promise, potential.  The poet in me imagines how
zero embodies that, mapping these states to -1, 0, and 1, respectively.

"But ttn, we're talking about Emacs Lisp and specifically binary data!"

Yes.  No one is born programmer or poet, yet both can hack (in) Emacs.
What is confusion but a stretching of the mind?  What is Emacs but
confusion, parenthesized and shared?

-- 
Thien-Thi Nguyen
GPG key: 4C807502

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Re: About "set bits"

[Barry Margolin]

In article <mailman.23943.1365669842.855.help-gnu-emacs@gnu.org>,
 Thien-Thi Nguyen <ttn@gnuvola.org> wrote:

> () Barry Margolin <barmar@alum.mit.edu>
> () Wed, 10 Apr 2013 11:37:19 -0400
> 
>    phrases as computer or Emacs jargon, when they just have the meaning
>    the words imply.
> 
> Assuming that one can parse "set bit" as ADJ N, there is still room for
> confusion.  Being around computers for a long time, i interpret "set" as
> "having value 1", but recognize anyway that such is not universal.
> 
> For example, in the phrase "ready, set, go", the state "set" gives the
> impression of suspense, promise, potential.  The poet in me imagines how
> zero embodies that, mapping these states to -1, 0, and 1, respectively.
> 
> "But ttn, we're talking about Emacs Lisp and specifically binary data!"
> 
> Yes.  No one is born programmer or poet, yet both can hack (in) Emacs.
> What is confusion but a stretching of the mind?  What is Emacs but
> confusion, parenthesized and shared?

True, these phrases can be ambiguous. But often the context and examples 
help quite a bit in figuring out the intent. In this case, there were a 
couple of examples; "bits" tells you to think in binary, and if you 
examined the binary values of the examples it should quickly become 
apparent what was meant.

-- 
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Re: About "set bits"

[Thien-Thi Nguyen]

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() Barry Margolin <barmar@alum.mit.edu>
() Thu, 11 Apr 2013 11:19:54 -0400

   True, these phrases can be ambiguous. But often the context and
   examples help quite a bit in figuring out the intent. In this case,
   there were a couple of examples; "bits" tells you to think in binary,
   and if you examined the binary values of the examples it should
   quickly become apparent what was meant.

Yes, i think if OP were to try more stuff in *scratch*, such questions
could be avoided.  In this case, i wrote examples that (to me) seem easy
to inspect and mentally verify, so that *scratch* is not even necessary.

(Although probably they could use some additional bit-field diagrams:

   1
   5      8 7      0
  ┌────────┬────────┐
  │00101000│00011100│  =>  (2 3 4 11 13)
  └────────┴────────┘
      28       1C

and

   1
   5      8 7      0
  ┌────────┬────────┐
  │00011100│00101000│  =>  (3 5 10 11 12)
  └────────┴────────┘
      1C       28

Let's hope people will step forward and improve the docs over time.)

-- 
Thien-Thi Nguyen
GPG key: 4C807502

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Re: About "set bits"

[Xue Fuqiao]

On Fri, 12 Apr 2013 06:39:17 +0200
Thien-Thi Nguyen <ttn@gnuvola.org> wrote:

> () Barry Margolin <barmar@alum.mit.edu>
> () Thu, 11 Apr 2013 11:19:54 -0400
> 
>    True, these phrases can be ambiguous. But often the context and
>    examples help quite a bit in figuring out the intent. In this case,
>    there were a couple of examples; "bits" tells you to think in binary,
>    and if you examined the binary values of the examples it should
>    quickly become apparent what was meant.
> 
> Yes, i think if OP were to try more stuff in *scratch*, such questions
> could be avoided.

Agreed.  Although I prefer *ielm*.

> In this case, i wrote examples that (to me) seem easy to inspect and
> mentally verify, so that *scratch* is not even necessary.

But I'm not familiar with binary files and binary code, I don't where to
start.

> Let's hope people will step forward and improve the docs over time.)

That's true.  Although my English isn't very good, I'd be glad to
improve/refine the documentation for Emacs, like proof-reading the
manuals and adding documentation about some packages/features that
aren't mentioned in the manuals.

-- 
Xue Fuqiao
http://www.gnu.org/software/emacs/