From: Caleb Clausen <vikkous@...>
Date: 2010-05-29T03:39:04+09:00
Subject: Re: A better way to write this function?

On 5/28/10, Jason Lillywhite <jason.lillywhite@gmail.com> wrote:
> Here is my attempt at Newton's second law in Ruby:
>
> #c is the drag coefficent
> #m is mass
> #t is total time elapsed
> #dt is time increment
> #vi is the starting velocity
>
> G = 9.8
>
> def velocity(c, m, t, dt, vi)
>   vel = []
>   t += dt
>   steps = t/dt
>
>   steps.times do
>     v = vi
>     vi = v + ( G - c/m*v) * dt
>     vel << v
>   end
>   return vel
> end
>
> Is there a better way to do write this function? It seems pretty
> straight forward to me so I guess that might be a sign that it is fine
> the way it is...?
>
> What if I needed more speed but still wanted it in Ruby?

A couple small speedups. c/m never changes while the loop is running,
so compute it once when the loop starts, then reuse the value. And you
could replace the times loop by a while loop for another small
speedup.... but this is never going to be fast in ruby. If you want
fast, use C.