--------------------------------------
 input != output -> see:part 5,same  
--------------------------------------
                                      
.................................
output : vec2d class computation 
.................................
 x,y component : vec2d(x,y)      
x coordinate vec2d(2,3) =  2
y coordinate vec2d(2,3) =  3
print : v1=vec2d(2,3)      
.................................
[2, 3]
 substraction : vec2d(5,3)-vec2d(3,1) =
.......................................
vec2d(5,3)-vec2d(3,1) = [2, 2]
 combination : vec2d(5,3)-2*vec2d(3,1) =
........................................
vec2d(5,3)-2*vec2d(3,1) = [-1, 1]
 output : is not list = 
 v3=vec2d(5,3)-2*vec2d(3,1)  [-1, 1]
<class '__main__.vec2d'>
make output :list       
 v4=[v3.x,v3.y] =  [-1, 1]
<class 'list'>
>>> %Run test9..py
--------------------------------------
 input != output -> see:part 5,same  
--------------------------------------
                                      
.................................
output : vec2d class computation 
.................................
 x,y component : vec2d(x,y)      
x coordinate vec2d(2,3) =  2
y coordinate vec2d(2,3) =  3
print : v1=vec2d(2,3)      
.................................
[2, 3]
 substraction : vec2d(5,3)-vec2d(3,1) =
.......................................
vec2d(5,3)-vec2d(3,1) = [2, 2]
 combination : vec2d(5,3)-2*vec2d(3,1) =
........................................
vec2d(5,3)-2*vec2d(3,1) = [-1, 1]
 output : is not list = 
........................
 v3=vec2d(5,3)-2*vec2d(3,1)  [-1, 1]
<class '__main__.vec2d'>
make output :list       
........................
 v4=[v3.x,v3.y] =  [-1, 1]
<class 'list'>