World: r3wp

how do you find the 4th part of a 4D vector?

ie. what comes after /z ?

4? :)

x, y and z can be possible, like we have first, second ...
To reach the next dimensions, integers are needed.
v: 1.0x2.0x3.0x4.0x5.0
v/x
1.0
v/5
5.0

A quick google took me to the Python page - "The 4th component can 
be accessed either by the name w or t." 

http://cgkit.sourceforge.net/doc2/vec4.html

First, second, ... go up to tenth. We don't have eleventh. You need 
to do serie/11 to get the 11'th element.

It would seem w is the popular choice - www.mathpages.com/home/kmath482.htm

Peter, ok idea, and I'm all for that. There just shouldn't be a limit, 
and we have to use integers to reach later parts of a vector ... 
like with series.

Good to know that is solved.

don't know why we just don't start with "a" and work our way thru 
to "z"

There also seems to be a convention of x y z t u v

We run out of characters giving meaning, if we have for example an 
8-dimensional vector. But it should be possible to make an 8-dimensional 
vector.

t, u and v is probably found a lot in 3D graphics math.

I'm sure that there is a mathematical convention and would be surprised 
if Carl S doesn't know it.

t for translation. u and v is used as uv-mapping of textures.

I don't even think, it'll take up much code to implement these things. 
The theory is there, and it's well-defined, how you calculate with 
vectors and matrices.

All different kinds of 3D manipulation will look simple, like scaling, 
rotation, reflection, etc. All those are well-defined matrix-operations. 
And supporting multi-dimensional vectors and matrices might pull 
a lot of science people to REBOL.

We need some different symbols for multiplication. dot-product, cross-product.

M: make matrix! 4x4
T: make matrix! 4x4
maybe: M x T
:-)

but x might be a word.

maybe
M * T for cross-product, and
M . T for dot-product?

Would it be strange to have dots flying around in the code, all by 
themselves?

Reaching second element on second row in a 2-dimensional matrix:
M/2x2

And of course we should have matrices with more than 2 dimensions, 
so something like this is possible:
M/2x2x2

So pairs need to be extended somehow into a datatype, which is like 
a vector, but with integers instead of decimals.

/joke-mode-on
Sorry guys, REBOL 3.0 is delayed another year! ;-)
/joke-mode-off

Hi! Why use pairs for idexing thats what paths are for. What is wrong 
with M/2/2/2   ?

we should stay with path imo ...

although we got overvoted for rebcode, which uses dot ;-)

since pairs are only integers not decimals vector and matrix could 
be replacement for draw dialect coordinates, AGG has subpixel accuracy

Karol: You can do 2x2 with pair! but not 2/2 with path!

like this: a: [ [ 0 1] [ 2.2 3.1]]  a/2/1

Geomol: "So pairs need to be extended somehow into a datatype, which 
is like a vector, but with integers instead of decimals." --- decimal! 
is better in my opinion. It's consistent with current behaviour whre 
you can do 
>> block/4.5
and decimal part is truncated.

but with matrix we can     a: make matrix! [ [ 0 1] [ 2.2 3.1]]  
a/2/1

if pair will be extended it overloads 16 byte limit for slot and 
become a series datatype, something complety different. there can 
be only 10 bytes per value ( I don't know exacly but tuples can have 
only 10 bytes not more)

during a bath, I thought up a Grand Master Plan:


1. Build a dialect that could handle scientific/symbolic math on 
the hard core level

2. Make it possible to take an equation and draw it up correctly 
with DRAW, a pretty print equation display. The same dialect would 
be used as above.

3. Use that to display pretty equations inline in makedoc2/3 documents!

4. Some people are working on a postscript dialect which hopefully 
eventually will be able to use DRAW blocks as an input, thereby allowing 
you to create equations on the console and convert it to DRAW or 
PS at the same time as having the ability to do calculations. That 
would be powerful.

Say:

calculate [2 [m] / 3 [cm]] ; would return the result as needed
calculate/draw [2 [m] / 3 [cm]] ; would return a DRAW block

postscript calculate/draw [2 [m] / 3 [cm]] ; would convert that DRAW 
block to postscript

now there is just the problem of doing symbolic math in such a block. 
you'd need specific functions for that, I think.

this is probably something that is best suited in another group...

Karol, I think, you're right. Path is ok with matrices too. M/2/2/2 
means the same as M/2x2x2, so no need for this new way.

Another application for matrices can be signal processing with native 
operators it could be possible to make things like jpeg compression, 
audio effects etc in plain rebol

And I think we have them already in Rebol ............ in AGG

Is it just me or does it seem Carl is trying to switch many things 
around in favor of newbies only?

:)

does it seem clear to me that the first thing rebol needs is more 
documentation?

We ALL are....

more in the sense of tutorials, guides and stuff... not references.

in a sense, I feel, some proposals from Carl stray away from rebol's 
current orthogonality ?

I mean anyone can re-implement first, second, third as pick 1, pick 
2, pick 3 if they want.   its dead easy.

No...you hit first....newbies....

No...nothing is easy, most people are stupid, and most peoplehere 
on Rebol3 are in teh 98+ percentile...  It just "feels" easy to you.

:)