Re: The Euphoria Sub Commander project
don cole wrote:
>
>
> Could someone please explain the following code to me in detail? I'm
> especially
> confused by the
> {} brackets.
>
> }}}
<eucode>
>
> k=player --1 or 2
> cen={{120,360},{520,360}}, -- centers of clock
Two clocks, center of 1 is {120,360} and the centre of 2 is {520,360}
> r=100, -- radius of clock
> rt=remaining time in secs
>
>
> Don Cole
>
> function p2xy(atom r, atom a) -- polar to xy
> return {-r*sin(a),-r*cos(a)}
> end function
>
> draw_line(colors[k],{cen[k],cen[k]+p2xy(r,rt/1800*PI)})
Draws a line from the centre of the clock to somewhere on the edge.
As sin/cos expect arguments in radians, 0..2*PI, and rt is 0..3600, the number
of seconds in an hour, it is coded as /1800*PI rather than /3600*2*PI.
Now imagine a clock with the second hand pointing at 10 seconds past the hour,
drop a line to the horizontal through the centre to make a right angled triange
whose longest side is the second hand. For a picture, see eg
http://www.mathsrevision.net/gcse/pages.php?page=39
From basic trig, the height of this triangle is r*sin(a) and the width is
r*cos(a). (I almost always get such the wrong way round on first attempt.)
Lastly, rt is the remaining time, a hand pointing at 2 o'clock would be
(10/12)*3600 or 3000 seconds which should explain why the offsets from the clock
centre to the tip of the arm are both returned as -ve.
Hope that is enough detail for you there,
Pete
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