[Haskell-cafe] bitSize

Alexander Kjeldaas alexander.kjeldaas at gmail.com
Mon Aug 29 10:08:10 CEST 2011

On 27 August 2011 21:57, Brandon Allbery <allbery.b at gmail.com> wrote:

> On Sat, Aug 27, 2011 at 06:57, Andrew Coppin <andrewcoppin at btinternet.com>wrote:
>> On 26/08/2011 10:51 PM, Steve Schafer wrote:
>>> On Fri, 26 Aug 2011 20:30:02 +0100, you wrote:
>>>> You wouldn't want to know how many bits you need to store on disk to
>>>> reliably recreate the value?
>>> I can't say that I have cared about that sort of thing in a very long
>>> time. Bits are rather cheap these days. I store data on disk, and the
>>> space it occupies is whatever it is; I don't worry about it.
>> I meant if you're trying to *implement* serialisation. The Bits class
>> allows you to access bits one by one, but surely you'd want some way to know
>> how many bits you need to keep?
>  I think that falls into the realm of protocol design; if you're doing it
> in your program at runtime, you're probably doing it wrong.  (The fixed size
> version makes sense for marshaling; it's *dynamic* sizes that need to be
> thought out beforehand.)
All search engines deal with compressed integers, all compressors do, and
most people doing bit-manipulation. Golomb, gamma, elias, rice coding, they
all need this. Heck, even the Intel engineers chose to optimize this
function by including the BSR instruction in the 386 architecture.  This is
a basic building block.

Don't underestimate the bit, it is coming back with a vengeance. Bit-coding
is everywhere now, because of the memory hierarchy.  No haskeller should be
left behind.

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