RE: global variables, or ...

[Richardson, Anthony]

> From: address@hidden [mailto:address@hidden On Behalf Of gary bollenbach
> 
> Hello All,
> Searching the forum archive for 'global variable' brings up 1186 posts.
> I've looked at
> the last 6 yrs, in summary at least.  Script still doesn't work.  I'm sure 
> there is
> something very elegant which would make it work.  Any advice?
> 
> thanks,
> GB
> 
> # physics problem
> 
> clear;
> 
> global a
> a = input( " What is the speed of the two trains, m/s [20]: " ); global b b =
> input( " How far apart are the trains when they spot each other, km [2]:
> " );
> 
> # (a) calculate the deceleration
> # -v^2/(2*y) = decel;
> global decel
> decel = (-a^2/2)*(2/(b*1000));
> 
> # (b) calculate the distance from decelerating train to impact point function 
> y
> = f(x)
>    global decel
>    global a
>    global b
> y(1) = decel/2*x(1)^2 + a*x(1) -x(2) + 0;
> y(2) = 0*x(1)^2 + a*x(1) +x(2) -b*1000;
> endfunction
> [x, fval, info] = fsolve(@f, [0; 0])
> 
> printf( " (a) The mutual, equal deceleration, m/s^s, is [-0.2]: %.4f \n", 
> decel );
> printf( " (b) The first x represents the time, s, to impact [58.6]. \n" ); 
> printf( "
> (b) The second x represents the distance, m, from the \n" ); printf( " (b)
> decelerating train start point to impact point [828]. \n" );

Seems to work okay for me (it runs, I haven't checked to see if the values are 
correct) after adding the line:

        function y = f(x)

to indicate the start of the function.  (Right before the second "global decel" 
line.)

Tony Richardson