>> That's apparently the Milner-Hindley type inference algorithm. But 
>> whatever.
> 
> That's what the file name says :D

I believe the correct response is "that's what SHE said!"

And besides, I named the file. (The website does some JavaScript 
trickery to make it maximally awkward to copy the image file. But they 
didn't bargin for the PrtSrc key...)

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Kevin Wampler wrote:

> I suppose I normally view distance in Euclidean space from the same 
> definition that applies to non-Euclidean spaces, rather than the 
> sqrt(dx^2 + dy^2) form, so I didn't really consider this.  You're right 
> though, if you're starting from the pythorgean theorem view of distance 
> it does bear some thinking about how it generalizes to the non-Euclidean 
> space.
> 
> That said, I'm not sure it's necessary to actually understand the proper 
> definition of distance in order to talk about circles in other spaces -- 
> particularly if we limit ourselves to spherical and hyperbolic spaces 
> which are more or less easy to visualize.

So how *do* you compute the distance between two points in a non-Euclid 
space anyway?

For that matter, is there a way to unambiguously refer to a specific 
point in such a space?

(Normally you would of course just use Cartesian coordinates, but it is 
not clear to me that this works any more once you remove the parallel 
postulate.)

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>> Interesting fact: In elliptic geometry, pi is less than arcsine 1.
> 
> It's less than arcsine 1 where you're sitting right now. That's why they 
> say gravity bends space-time.

Space-time is an inhomogenous space anyway. I hear that gravity bends it 
with positive curvature, but the universe itself appears to have 
slightly negative curvature...

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> Erm... 1.6L means that the engine block has a displacement of 1.6L, while 
> 2.3L means that the displacement is 2.3L - i.e., the cylinders are 
> physically bigger.

It used to be like that, if you bought a "one point six" it meant the engine 
displacement was roughly 1600 cc, but nowadays car makers like to keep the 
"one point six" naming convention but actually have a standard engine 
displacement across all models.  A bit like how AMD called their processor 
an XP2400, but it wasn't 2400 MHz.  If I'd bought the "1.6" version of my 
car it would have exactly the same engine as the "2.0" version, displacement 
1998cc.

> The Real WTF of course is that displacement is not directly related to 
> power output in the first place...

There are a vast number of things that significantly affect power output 
apart from displacement.  A useful quantity is "horsepower per litre" to 
compare engines.  Really efficient road-car engines can get up to 100 
HP/litre, racing engines over 300 hp/litre.

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scott wrote:
>> Erm... 1.6L means that the engine block has a displacement of 1.6L, 
>> while 2.3L means that the displacement is 2.3L - i.e., the cylinders 
>> are physically bigger.
> 
> It used to be like that, if you bought a "one point six" it meant the 
> engine displacement was roughly 1600 cc, but nowadays car makers like to 
> keep the "one point six" naming convention but actually have a standard 
> engine displacement across all models.  A bit like how AMD called their 
> processor an XP2400, but it wasn't 2400 MHz.  If I'd bought the "1.6" 
> version of my car it would have exactly the same engine as the "2.0" 
> version, displacement 1998cc.

Sure, but AMD don't actually call it the XP 2.4GHz. That would be false 
advertising - as would claiming that an engine has a displacement of X 
when it's actually Y.

>> The Real WTF of course is that displacement is not directly related to 
>> power output in the first place...
> 
> There are a vast number of things that significantly affect power output 
> apart from displacement.  A useful quantity is "horsepower per litre" to 
> compare engines.  Really efficient road-car engines can get up to 100 
> HP/litre, racing engines over 300 hp/litre.

Or just HP if you want to know how powerful it is, MPG if you want to 
know how efficient it is... I never did understand the fascination with 
displacement. (Other than that I guess you can unambiguously measure it.)

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> Sure, but AMD don't actually call it the XP 2.4GHz. That would be false 
> advertising - as would claiming that an engine has a displacement of X 
> when it's actually Y.

Yeh, I doubt any car makers falsely advertise the displacement.  But calling 
your car a "1.6 TDI" or whatever and it actually having a displacement of 
2000cc is probably ok (even though 90% of people would assume the 
displacement was 1.6 litres).

> Or just HP if you want to know how powerful it is,

I doubt many people are actually interested in the maximum power their 
engine can develop at one particular engine speed.  What's more useful is 
how quickly the car can accelerate, eg 40-70mph or 70-100mph times.  This 
depends on how much power the engine can develop across a wider range of 
RPMs, and also the mass of the car.

> MPG if you want to know how efficient it is... I never did understand the 
> fascination with displacement. (Other than that I guess you can 
> unambiguously measure it.)

Didn't the UK car tax depend on the displacement of your engine?  Also lots 
of racing formulas have limits on the engine displacement (eg 2400cc for F1 
currently).  The HP/litre figure is also a good guide as to how well 
engineered and advanced the engine is.  And of course higher displacement 
usually means a heavier engine, which is something you usually try to avoid.

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scott wrote:
>> Sure, but AMD don't actually call it the XP 2.4GHz. That would be 
>> false advertising - as would claiming that an engine has a 
>> displacement of X when it's actually Y.
> 
> Yeh, I doubt any car makers falsely advertise the displacement.  But 
> calling your car a "1.6 TDI" or whatever and it actually having a 
> displacement of 2000cc is probably ok (even though 90% of people would 
> assume the displacement was 1.6 litres).

Hmm, probably.

I'm pretty certain my car's engine *really is* 1.6L though. (The Haynes 
manual has different instructions depending on the size and/or year.)

>> Or just HP if you want to know how powerful it is,
> 
> I doubt many people are actually interested in the maximum power their 
> engine can develop at one particular engine speed.  What's more useful 
> is how quickly the car can accelerate, eg 40-70mph or 70-100mph times.  
> This depends on how much power the engine can develop across a wider 
> range of RPMs, and also the mass of the car.

Or that, yes.

I still find it quite impressive that a CAR, which is made of METAL and 
powered by EXPLODING PETROL, can apparently be out-accelerated by a 
cheetah, which is MADE OF MEAT. Then again, an adult cheetah probably 
weighs significantly less than an Audi TT...

>> I never did understand 
>> the fascination with displacement. (Other than that I guess you can 
>> unambiguously measure it.)
> 
> Didn't the UK car tax depend on the displacement of your engine?

Ah yes, if your car is 1.1L or less, you get cheaper car tax.

Presumably the government chose this value since all 1.1L cars known to 
man are actually 1103 cc, not 1100 cc. Hence, approximately 0.1% of the 
population qualify for this.

In any case, given that this is supposedly a "green tax", taxing based 
on emissions or fuel efficiency would seem far more logical. But then, 
the entire concept that you can make people abandon their cars just by 
making it too expensive is laughable. You make people use alternatives 
by making the alternatives ACTUALLY ****ING WORK, not just by taxing 
them off the road. But then, the former costs money, while the latter 
generates money under the pretenses of giving a **** about green, so...

> Also 
> lots of racing formulas have limits on the engine displacement (eg 
> 2400cc for F1 currently).

Yes. Presumably so that to make the car go faster, you have to actually 
*work at it* rather than just make it burn petrol faster. ;-)

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Stephen wrote:
> Eero Ahonen wrote:
> 
>>  - still having
>> 150bhp/320Nm (upgradeable to 175bhp/370Nm with just a software) with
> 
> Let’s have an argument about the difference between hp and bhp, please. :-P
> 

Bhp is a more defined unit than hp - bhp is the actual power that comes
out of the engine (and goes to the gearbox).

Well, actually bhp should be "braked" from the car itself - and they
will be, after I'll upgrade the software.

-Aero

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scott wrote:
> 
> Aren't all cars upgradeable with just software nowadays?  

Yes. Actually even my '89 9000 has upgraded software.

> In my car the
> "1.6L", "1.8L", "2.0L" and "2.3L" versions all actually have exactly the
> same engine.  

No, they are not :). The very basic engine (=the block itself) is the
same, yes.

> You are just choosing whether you want the 116, 143, 177
> or 204 BHP software installed when you buy it :-)  

Nope. The 123d has two turbochargers. The 120d has a bigger
turbocharger, different injectors, IIRC different crankshaft and some
other differencies compared to 118d. 118d and 116d may possibly be the
same engine, I haven't found theier differencies, but I'd guess that
they too have different turbos.

Yes, 1-series was one of the possibilities I though about, so I did a
little digging :p.

> I heard some people
> got up to 265 BHP out of that engine, but to me that seems really stupid
> as all the other components will not have been reliability tested at
> that power level.

I'd say that if it's done correctly, the reliability shouldn't be a
major problem on that engine (especially 123d). But the software I
referred to is a official software (by Hirch), so it won't trash the
warranty of the car.

-Aero

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Invisible wrote:
> I still find it quite impressive that a CAR, which is made of METAL and 
> powered by EXPLODING PETROL, can apparently be out-accelerated by a 
> cheetah, which is MADE OF MEAT. Then again, an adult cheetah probably 
> weighs significantly less than an Audi TT...

And probably by a lightly loaded large commercial jet, for that matter.

-- 
Darren New, San Diego CA, USA (PST)
   Forget "focus follows mouse." When do
   I get "focus follows gaze"?

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