On Wed, 25 Aug 2010 10:28:25 +0100, Orchid XP v8 wrote:

>>>>> Binary shifts are multiplication and division as well. :P
>>>> What you want is binary rotations. ;-)
>>> That depends on whether the bits actually get rotated.  From my
>>> recollection of x86 assembly, it's a shift, not a rotation. :)
>>>
>>> Jim
>> 
>> My recollection, of course, has changed now that I re-read this, I
>> remember ROR and ROL operators, which do in fact rotate.  I just
>> remember using SHL and SHR more frequently.
> 
> Whether your processor supports it or not, binary rotations exist. You
> can implement them the hard way if you must. I've seen a few block
> ciphers that use 'em too...

Well, that's why I said what I said about my faulty recollection. ;-)

Jim

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On 8/23/2010 2:47 PM, Darren New wrote:

> Metric has the advantage that you don't get into weird problems with
> units when you do science. I don't think it really matters that things
> are specifically multiples of 10 until you start getting into figuring
> out ranges of numbers where exponents come into play.

If you've taken physics, the real help comes in the fact that the 
majority of units are some multiple of other units with no other factors 
to throw in (and thus, misremembered at times).

For example, one Watt (unit of power) is equal to one Joule (unit of 
energy) per second.  One horsepower (imperial unit of power) is equal to 
some silly number of foot-pounds per second.

Regards,
John

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John VanSickle wrote:
> For example, one Watt (unit of power) is equal to one Joule (unit of 
> energy) per second.  One horsepower (imperial unit of power) is equal to 
> some silly number of foot-pounds per second.

Sure. That comes from having only one unit of measurement for each 
fundamental thing you're measuring. On the other hand, you still get some 
arbitrary factors in there, like moles or parsecs.

If I asked you how much power it took to lift what a horse could, or how 
many pounds of force you had to push a foot-long lever with, you'd once 
again have those arbitrary scale factors thrown in. ;-)

I'm not saying metric isn't easier. I'm pointing out that imperial stuff, 
since it's based on people, is very poor at measuring things that aren't 
approximately relevant to people, like the weight of planets or the size of 
atoms.

-- 
Darren New, San Diego CA, USA (PST)
    Quoth the raven:
        Need S'Mores!

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Darren New <dne### [at] sanrrcom> wrote:
> I'm not saying metric isn't easier. I'm pointing out that imperial stuff,
> since it's based on people, is very poor at measuring things that aren't
> approximately relevant to people, like the weight of planets or the size of
> atoms.

It's not just that: imperial isn't precise.  I asked before and it was ignored,
but should I measure 10 foot to be the distance traveled by my 10 of my steps or
10 of my daughter steps?

Besides, you need to put true mental calculations at work to convert between
units, instead of simply moving the point forward or backwards between
centimeters, meters and kilometers...

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nemesis wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> I'm not saying metric isn't easier. I'm pointing out that imperial stuff,
>> since it's based on people, is very poor at measuring things that aren't
>> approximately relevant to people, like the weight of planets or the size of
>> atoms.
> 
> It's not just that: imperial isn't precise.  I asked before and it was ignored,

Well, *now* it is precise. Obviously it wasn't precise when it was 
formulated.  I think the foot, however, was the size of some specific king's 
foot. And the metric measurements have changed definitions over the years as 
well.

> Besides, you need to put true mental calculations at work to convert between
> units, instead of simply moving the point forward or backwards between
> centimeters, meters and kilometers...

Sure, because there are different units, unlike the SI measurements which 
only have one unit per fundamental element being measured. I still have to 
put mental calculations forth to translate between seconds and meters, or 
between meters and light-years, or between watt-hours and watt-months, or 
between moles and grams, because they're different units based on arbitrary 
physical properties. The fact that one has to translate between inches and 
feet isn't really any more of a problem than the fact that metric 
measurements have to translate between seconds and years.

-- 
Darren New, San Diego CA, USA (PST)
    Quoth the raven:
        Need S'Mores!

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On 29/08/2010 12:53 AM, Darren New wrote:
>
> Well, *now* it is precise. Obviously it wasn't precise when it was
> formulated.  I think the foot, however, was the size of some specific
> king's foot. And the metric measurements have changed definitions over
> the years as well.
>

Henry I of England, but not his bare foot.

>> Besides, you need to put true mental calculations at work to convert
>> between
>> units, instead of simply moving the point forward or backwards between
>> centimeters, meters and kilometers...
>
> Sure, because there are different units, unlike the SI measurements
> which only have one unit per fundamental element being measured. I still
> have to put mental calculations forth to translate between seconds and
> meters, or between meters and light-years, or between watt-hours and
> watt-months, or between moles and grams, because they're different units
> based on arbitrary physical properties. The fact that one has to
> translate between inches and feet isn't really any more of a problem
> than the fact that metric measurements have to translate between seconds
> and years.

I would say less of a problem, actually. Constantly doing mental 
arithmetic helps keep the mind active. I’ve noticed, here in the UK, the 
lack of ability in young people who grew up learning the metric system. 
I assume that they did not have to do sums like:
What is the cost of 3 yards 1 foot of material @ 2/6 a yard.

Ans: 8/4 That is 8 shillings and 4 pence.

-- 

Best Regards,
	Stephen

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Le 29/08/2010 11:17, Stephen nous fit lire :
> On 29/08/2010 12:53 AM, Darren New wrote:
>>
>> Well, *now* it is precise. Obviously it wasn't precise when it was
>> formulated.  I think the foot, however, was the size of some specific
>> king's foot. And the metric measurements have changed definitions over
>> the years as well.
>>
> 
> Henry I of England, but not his bare foot.
> 
>>> Besides, you need to put true mental calculations at work to convert
>>> between
>>> units, instead of simply moving the point forward or backwards between
>>> centimeters, meters and kilometers...
>>
>> Sure, because there are different units, unlike the SI measurements
>> which only have one unit per fundamental element being measured. I still
>> have to put mental calculations forth to translate between seconds and
>> meters, or between meters and light-years, or between watt-hours and
>> watt-months, or between moles and grams, because they're different units
>> based on arbitrary physical properties. The fact that one has to
>> translate between inches and feet isn't really any more of a problem
>> than the fact that metric measurements have to translate between seconds
>> and years.
> 
> I would say less of a problem, actually. Constantly doing mental
> arithmetic helps keep the mind active. I’ve noticed, here in the UK, the
> lack of ability in young people who grew up learning the metric system.
> I assume that they did not have to do sums like:
> What is the cost of 3 yards 1 foot of material @ 2/6 a yard.
> 
> Ans: 8/4 That is 8 shillings and 4 pence.
> 

Why stop at only mental activity, let's also take into account the year
of mint, as it used to be.
And each mint (and that could each city) could have its own agenda for
the weight of its pounds & guinea.

May be I can slice some pounds in two, or scrap enough of them to make a
new one...

Shilling has been dropped in 1971... and the penny is now decimal.
But we can mix pound, shilling (at 20 per pound), pences (at 240 per
pound) and new pences (at 100 per pound) with guinea (1 pound 1 shilling)

Oh, I call in the Bretton Woods system, in which I could exchange 1
pounds for $4.03...

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On 29/08/2010 10:49 AM, Le_Forgeron wrote:
> Why stop at only mental activity, let's also take into account the year
> of mint, as it used to be.
> And each mint (and that could each city) could have its own agenda for
> the weight of its pounds&  guinea.
>

Now you are being silly. ;-)

> May be I can slice some pounds in two, or scrap enough of them to make a
> new one...
>

That is why coins are milled. To stop people like you shaving or 
clipping coins. :-P

> Shilling has been dropped in 1971... and the penny is now decimal.
> But we can mix pound, shilling (at 20 per pound), pences (at 240 per
> pound) and new pences (at 100 per pound) with guinea (1 pound 1 shilling)
>

But some of us remember the days of L.s.d. man ;-)

> Oh, I call in the Bretton Woods system,

Morning town Crescent!

> in which I could exchange 1
> pounds for $4.03...

I remember my father calling a half crown (12.5p) a half dollar.

-- 

Best Regards,
	Stephen

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Le_Forgeron wrote:
> And each mint (and that could each city) could have its own agenda for
> the weight of its pounds & guinea.

Well, yes. There's also the problem with imperial measures that the king 
would go around declaring that a barrel in London is somewhat larger than a 
barrel outside of London, thereby lowering the cost of beer in the capital 
city and stuff like that.

-- 
Darren New, San Diego CA, USA (PST)
    Quoth the raven:
        Need S'Mores!

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On 29-8-2010 1:53, Darren New wrote:
> nemesis wrote:
>> Darren New <dne### [at] sanrrcom> wrote:
>>> I'm not saying metric isn't easier. I'm pointing out that imperial 
>>> stuff,
>>> since it's based on people, is very poor at measuring things that aren't
>>> approximately relevant to people, like the weight of planets or the 
>>> size of
>>> atoms.
>>
>> It's not just that: imperial isn't precise.  I asked before and it was 
>> ignored,
> 
> Well, *now* it is precise. Obviously it wasn't precise when it was 
> formulated.  I think the foot, however, was the size of some specific 
> king's foot. And the metric measurements have changed definitions over 
> the years as well.

Such changes occur for good reasons. E.g. in the triple 
time/velocity/length you can define any two and the third can then be 
measured. Originally the speed of light was the quantity to measure. 
Nowadays that is a constant, otherwise the theoretical physicists would 
be very upset.
If you define the length then you can measure how long one second is. Or 
you define a meter and then you can measure how much time a photon takes 
to traverse that distance. Which one you choose simply depends on what 
you can measure most accurately. If your error in a meter is, say, one 
in 10^12 and in a second it is one in 10^10, it is unwise to take the 
second as definition, because the maximal achievable precision of a 
length measurement will then drop to one in 10^10.

I hope all imperial units are now defined as fractions of the metric 
ones or we will need two committees to decide when to change the places 
of meters and seconds. However, if you look at the wiki page about 
imperial units some conversions are exact, whereas others are given to 
be exact to 4 or 5 decimal places. Much larger than the scientific 
uncertainty in the values, so that supports nemesis' claim, although 
perhaps not in the way he/she meant.

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