[boost] Re: Physical quantities

From: Andy Little (andy_at_[hidden])
Date: 2004-01-15 16:32:57

"Deane Yang" <deane_yang_at_[hidden]> wrote
> Andy Little wrote:
> > "Deane Yang" <deane_yang_at_[hidden]> wrote

[snip]

> > You say you understand the mathematical concepts behind dimensional
> > analysis. I am not qualified to tell if you do or you dont. However if
you
> > do, it would be extremely useful if you wrote a paper on the subject.
>
> If you go back to the first posting whose subject contained "(long
> reply)", I described all the essential details (just start reading
> after "let's review"). There's really nothing more to dimensional
> analysis than that.

Oh that post . The one that starts by asking me a question:

"Isn't the whole point of dimensional analysis to derive
the dimension and units of PQout_t from the two input factors?"

Sorry I couldnt be bothered to reply. The answer is... No, that is not the
point of dimensional analysis.

I actually thought you meant this post. the part of that which I understand
is:
"
None of this helps anyone do anything; nobody really needs to know any
of this.
"
If you dont understand the basics, then by definition, the rest of your
'long reply' post is <****>.

Hey look I am seriously Not attempting to be negative, regarding the earlier
post. I have a vague idea of what a tensor is. AFAIK it is a fancy word for
a matrix. (from studying  Walter Landrys "Implementing a High Performance
Tensor Library"  doc). In this context, I would tend to use the word array,
because it is more universally comprehensible to someone like me who
programs C++. Then again, in my definitions I have used the word set, as
there is no particular ordering.

Your use of the word tensor is a classic example of taking  concepts from
the 'advanced concepts' shelf where one from the 'simple concepts' shelf
will do. Further, you have possibly unknowingly used SI terms. You use
different terms to refer to the same thing. Not two but three.If I really
wanted to be rude I would replace description of your work as 'precise '
with the word 'lazy'.

Try Here.
http://www.servocomm.freeserve.co.uk/Cpp/physical_quantity/PhysicalQuantities1.html

I dont claim that this is correct, but is one example of how to approach
this subject. I hope to base all my documentation on those definitions and
the next version of the physical-quantities type. I may call the next
version 'quantities', as I have started to pull the logic out and abstract
it. The doc above has been revised several times and will need more. Where
you currently see 'physical-quantity' I may replace with 'quantity'.
Unfortunately the rest of the documentation must be revised to refer to that
doc.( Ie The rest of the docs use old/wrongly named terms... which I hope to
correct If I can ever get off this newsgroup.)

I  believe that in your own mind  you  know what you are talking about, but
to communicate to someone like me, you will need to do a great deal more
work than I have currently seen.

> So if you really want to understand what I am saying (I admit I probably
> usually say too much), just read that one posting very carefully. Feel
> free to ask me questions.

OK ?

regards
Andy Little