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gene_sullivan@[EMAIL PROTECTED]
In LogoForum@[EMAIL PROTECTED]
"jbhnj1975" <jbhnj1975@[EMAIL PROTECTED]
> wrote:
>
>
>
> I would like to start with something simple like an xy plane graphing a
> parabola as y=(+/-)x^2
>
> Can I create a program (in Elica/Logo) that can solve and graph
> equations?
>
> I assume I would need to label the variables and put in limits..
>
> Any ideas?
Sure.
If you're new to Logo but have the grounding in Cartesian coordinate
systems which the formulation of your question reveals, the turtle
moves in the XY plane by default. So, whether you are aware of not,
all that is lacking for you to `see' it as such are a pair of axes.
Every logo implementation I'm aware of has a `home' command which
places the turtle at (0,0).
Though most graphics are done with `forward' and `back', one may
use Cartesian coordinates as well.
One may find out the position of the turtle (EG a `cursor', if you
think about it) with either:
pos
turtle.pos
One may set the turtle's position directly (without doing Penup
followed by a `forward' or `back') by
setpos [x y]
where x and y are what you'd expect.
Notice the lack of comma, though; whitespace separates them.
{aside: The square brackets are those of a Logo list.
So one can form a separate list as a variable then
provide the name of the variable containing the list.
}
So, here is a little Elica program you should be able to copy
and paste into either a new file or the command window:
;v--- sample code bounded by this line
clearscreen
home
print pos
setpos [10 10]
print pos
;^--- sample code bounded by this line
However, to make sure you see the values of X and Y
which were printed out the print commands make sure
you have the `output' window visible.
This can be done with View -> Output
The position after `home' should be [0 0]
And the position of the turtle/graphics_cursor after
setpos [10 10] should be [10 10], obviously.
Given that the coordinates used by `setpos' may
be variables, one may set up one or more loops
in which variables may be changed and applied to
the arguments/parameters list of `setpos'
Here is another sample to run:
;v--- sample #2 code bounded by this line
clearscreen
home
print pos
make "len 10
make "angle 5
rt 90 ; set heading down positive X axis
repeat 20 [
fd :len
lt :angle
make :len (:len + 3)
make :angle (:angle * 1.5)
]
;^--- sample #2 code bounded by this line
Note that this --^ used fd and lt to draw, using conventional
turtle geometry.
Elica refers to this mode of drawing as `traditionalturtle'
However one can generate points using the `point' command.
However this might require that one `run graphix' first, which
you might not want to dabble in yet. So I created this one
which uses `setpos'
;v--- sample #3 code bounded by this line
clearscreen
home
print pos
make "delta_x 5
make "delta_y 2
make "this_x :delta_x
make "this_y :delta_y
repeat 10 [
setpos (list :this_x :this_y)
print pos
make "this_x (:this_x + :delta_x + 3)
make "this_y ((:this_y + :delta_y) * 1.5)
]
;^--- sample #3 code bounded by this line
Though this produces something roughly parabolic, I'll
leave the details of how you choose to graph your
parabola up to you.
I hope this helped in some way.
BTW. This group seems to be biased towards MSWLogo.
So you might get a better response from sending
Elica-specific questions to Elica's user group.
http://tech.groups.yahoo.com/group/elica/
Cheers!
Gene
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