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Re: [lojban] Re: Direction of Rotation



Am 25.08.2012 11:46, schrieb Robin Lee Powell:
On Fri, Aug 24, 2012 at 01:25:56PM +0200, selpa'i wrote:
[snip]
Thus, since all we need to define the direction is an axis ML,
which has an inherent orientation as mentioned above, and a point
B *relative* to our starting orientation towards AL', {carna},
which has both these as x2 and x3 respectively is plenty to
express clockwise and counter-clockwise motion. carna2 will not
need to be specified for bodies that overlap almost completely
with the axis ML, like for instance a standing human being, and
for objects like a disk that's lying flat on the plane, we only
need to choose the polarity of vector ML.

The problem is that you've ignored the hard part: how to specify the
vector ML.

I didn't so much ignore it as assume it wasn't the main point of importance here. I tried to make clear why it's almost never necessary to specifiy it.

We have, to the best of my knowledge, no compact way to do that *at
all*.

So you're saying the inventors created gismu places without any idea of how to fill them?

There are different ways. We can use the brivla relnacmei:

(1) mi carna lo relnacmei be lo mi jamfu bei lo mi stedu lo pritu
"I turn around the axis that is defined by a vector from my feet to my head in the direction of something to the right of what I'm currently facing." (who said lojban was verbose? :P )

And mekso has vector-support as well:

(2) mi carna li jo'i mo'e lo mi jamfu mo'e lo mi stedu lo pritu

Sentence (2) would be shorter if JOhI was allowed to take sumti, sort of like NUhI, which would look like Sentence (3).

(3)* mi carna jo'i lo mi jamfu lo mi stedu te'u lo pritu

Note that these vectors are not within a strictly mathematical space here, so mathematicians might complain. They are very easy to use, however, as you can see.

At the end you talk about specifying only the polarity; I
don't even know how to do *that* in compact fasion.

Both the above examples specify the "polarity" (direction) of the axial vector by means of order. The vector starts from the first point and moves in direction of the second point.

How do you specify "rotate the monitor clockwise as viewed from the
front" versus "rotate the monitor clockwise as viewed from right
side"?

(4a) ko cargau lo vidni zu'i lo pritu
"Rotate the screen clockwise around the default axis, which is the one orthogonal to the screen."

(4b) ko cargau lo vidni fi lo pritu fe lo se farna be da poi crane [vo'e]
"Rotate the screen clockwise around the axial vector that is oriented towards the front [of the screen]"

(4c) ko cargau lo vidni fi lo pritu fe lo se farna be da poi pritu [vo'e]
"Rotate the screen clockwise around the axial vector that is oriented towards the right [of the screen]

Or using ma'i:

(5) ko cargau lo vidni fi lo pritu ma'i lo crane/pritu be vo'e

One could even make lujvo for all these different "vectors":

craselfa'a   = x1 se farna lo crane be x2 [bei x3]
prityselfa'a = x1 se farna lo pritu be x2 [bei x3]
rixselfa'a   = x1 se farna lo trixe be x2 [bei x3]

and so on, which makes the sentence even shorter.

(6) ko cargau lo vidni lo craselfa'a lo pritu
    "Rotate the screen around the front-vector in clockwise direction."

So I stand by the fact that carna is sufficient as is (but I won't stop you from making a new word if that is what you desire).

mu'o mi'e la selpa'i

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