Solar system simulation using vpython

from visual import *
import time

class solor_system:
 
    def __init__(self):
        scene.width=1000
        scene.height=800
        scene.autoscale=0
        scene.range=(100,100,100)
        scene.center=(0,0,0)
       
        self.sun = sphere(pos=(0,0,0), radius=6, color=color.red,material=materials.emissive)
        lamp = local_light(pos=(0,0,0), color=color.orange)

        self.mercury = sphere(pos=(0,0,0), radius=1, color=color.green)
        self.venus = sphere(pos=(0,0,0), radius=1.5, color=color.blue)
        self.earth = sphere(pos=(0,0,0), radius=2, color=color.yellow,material=materials.earth)
        self.mars = sphere(pos=(0,0,0), radius=2.5, color=color.orange)
        self.jupiter = sphere(pos=(0,0,0), radius=3, color=color.cyan)
        self.saturn = sphere(pos=(0,0,0), radius=3.5, color=color.magenta)
        self.uranus = sphere(pos=(0,0,0), radius=4, color=color.white)
        self.neptune = sphere(pos=(0,0,0), radius=4.5, color=color.blue)
        self.pluto = sphere(pos=(0,0,0), radius=5, color=color.cyan)
       
        self.mercury_angle = 0
        self.venus_angle = 0
        self.earth_angle = 0
        self.mars_angle = 0
        self.jupiter_angle = 0
        self.saturn_angle = 0
        self.uranus_angle = 0
        self.neptune_angle = 0
        self.pluto_angle = 0
       
    def create_orbit(self):
       
        self.mercury.trail = curve(color=color.white)
        self.venus.trail = curve(color=color.white)
        self.earth.trail = curve(color=color.white)
        self.mars.trail = curve(color=color.white)
        self.jupiter.trail = curve(color=color.white)
        self.saturn.trail = curve(color=color.white)
        self.uranus.trail = curve(color=color.white)
        self.neptune.trail = curve(color=color.white)
        self.pluto.trail = curve(color=color.white)

    def draw_ellipse(self,x, y, a, b, angle, steps,ball,i):
        if steps == None:
            steps = 36
            # Angle is given by Degree Value
        beta = -angle * (math.pi / 180); #(Math.pi/180) converts Degree Value into Radians
        sinbeta = math.sin(beta);
        cosbeta = math.cos(beta)
        
        time.sleep(0.01)
        alpha = i * (math.pi / 180)
        sinalpha = math.sin(alpha)
        cosalpha = math.cos(alpha)
       
        X = x + (a * cosalpha * cosbeta - b * sinalpha * sinbeta)
        Y = y + (a * cosalpha * sinbeta + b * sinalpha * cosbeta)
        
        ball.x=(X)
        ball.y=(Y)
               
        
        ball.trail.append(pos=ball.pos)
       

    def main(self):
        self.create_orbit()
        while True:
            self.draw_ellipse(0,0,20,10,0,None,self.mercury, self.mercury_angle)
            self.mercury_angle = (self.mercury_angle + 5) % 360
            self.draw_ellipse(0,0,25,15,0,None,self.venus, self.venus_angle)
            self.venus_angle = (self.venus_angle + 4.5) % 360
            self.draw_ellipse(0,0,30,20,0,None,self.earth,self.earth_angle)
            self.earth_angle = (self.earth_angle + 4) % 360
            self.draw_ellipse(0,0,35,25,0,None,self.mars,self.mars_angle)
            self.mars_angle = (self.mars_angle + 3.5) % 360
            self.draw_ellipse(0,0,40,30,0,None,self.jupiter,self.jupiter_angle)
            self.jupiter_angle = (self.jupiter_angle + 3) % 360
            self.draw_ellipse(0,0,47,37,0,None,self.saturn,self.saturn_angle)
            self.saturn_angle = (self.saturn_angle + 2.5) % 360
            self.draw_ellipse(0,0,55,45,0,None,self.uranus,self.uranus_angle)
            self.uranus_angle = (self.uranus_angle + 2) % 360
            self.draw_ellipse(0,0,65,55,0,None,self.neptune,self.neptune_angle)
            self.neptune_angle = (self.neptune_angle + 1.5) % 360
            self.draw_ellipse(0,0,80,70,0,None,self.pluto,self.pluto_angle)
            self.pluto_angle = (self.pluto_angle + 1) % 360


if __name__=='__main__':
    ss=solor_system()
    ss.main()

creating shared library with simple example

1.create a separate folder to try this examples.

2. create the a main c file , another two c files which contain the functions used in the main file.

3. create the relative header file.
4.create the include folder and move your header file into that.
5.create the lib folder where we are going to place the our shared library.
6.say for example our files named as
main.c
func1.c
func2.c
lib/
include/

7.create the object file for both func1.c and func2.c using the below command

    gcc -Wall -fPIC -I include/ -c func1.c
    gcc -Wall -fPIC -I include/ -c func2.c

options:

-Wall:- include warnings
-fPIC:- Compiler directive to output position independent code, a        characteristic required by shared libraries

8.create the shared library using the following command.

    gcc -shared -Wl,-soname,libfunc.so -o libfunc.so *.o

options:

-shared:-Produce a shared object which can then be linked with other objects to form an executable.
-Wl:-Pass options to linker(eg--soname,libfunc.so)

9.move that created library file to lib folder
10.create  the  final executable using command

     gcc -Wall -I include/ -L lib/ -lfunc  main.c -o  main

11.normally when executing the final executable file, linker will look into the  /lib, so we have include our library path in the default searching path.


   export LD_LIBRARY_PATH=/path/to/our_lib_folder
12.now run the final executable..

Music and Browsing with emacs

Play music with emacs:

•       Download the mpg123 player using apt-get install command.
•       Download the emacs lisp function source code from here.
•       Untar the source, inside the directory you will find the file called 'mpg123.el'.
•       Copy that file and paste into the folder /usr/share/emacs/site-lisp.
•       Create the file .emacs into the home folder.
•       Add the following text in that (autoload 'mpg123' "mpg123" "A Front end to mpg123" t)
•       Save that file and open the emacs.
•       Enter the key stroke M+x mpg123 and you will ask for the folder where  the music files are available.

Browsing with emacs:

 w3m is text based browser can be used in terminal .

•      Download 'w3m-el' package using apt-get command.
•      Open emacs and enter the key stroke M+x w3m.
•      It will ask for the url and enter the url.
•      Now you can browse through the text version of web page.