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Re: Refreshing grade school math.

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Den söndag 12 januari 2020 kl. 07:13:13 UTC+1 skrev Julio Di Egidio:
> On Saturday, 11 January 2020 14:09:55 UTC+1, Jonas Thörnvall  wrote:
> 
> > This is what i try to do but without use of cosinus and sinus.
> 
> LOL.  To begin with, my congratulations for some reasonably readable
> code.  That said, and nitpicking aside (e.g. on the still too prominent
> use of globals, as well as probably some plain forgetting of the var
> keyword on some locals), I'd raise a couple of main points:
> 
> Firstly, I think it's messed up with nodes vs arr: on the first line
> you are using nodes as a count, later you count m up to arr.length,
> where arr I must guess is a global: this is too messy, either one or
> the other.  Indeed, to make it clean, I would suggest that all you
> actually need is a function that gets a count in input, the count of
> distinct points, and returns a brand new array with the needed
> coordinates, whose length of course will be that count.  (And,
> printnode looks like an indirect index: but your function shouldn't
> be bothered with "external" considerations, i.e. just build and
> return an array and rather do that on the caller's side if you
> really need.  At least, from what I can gather...)  (Plus, those
> radius and offsets better be defined in some outer scope, even be
> globals if nothing else, anyway not hard-coded into the function.)
> 
> Secondly, that logic of calculating the single step, then adding it
> repeatedly, plain accumulates floating-point errors, so it is not the
> way to write such a loop.  What you rather do is:
> 
>   var sect = 2 * Math.PI / count;
>   for (var m = 0; m < count; ++m) {
>     var theta = sect * m;
>   ...
> 
> You still get a minimum of floating-point error there, but it will
> not accumulate.
> 
> Also, you do not usually need to round off coordinates, certainly
> not for drawing.  If you thought pixel coordinates on a canvas are
> integers, note that they aren't...
> 
> > function circleNodes(nodes) {
> >     var step = 2 * Math.PI / (nodes);
> >     var h = 670;
> >     var k = 370;
> >     var r = 320;
> >     theta = 0;
> >     for (var m = 0; m < arr.length; m++) {
> >         nodeout = printnode[m];
> >         var MX = h + r * Math.cos(theta);
> >         var MY = k - r * Math.sin(theta);
> >         arr[nodeout].rposX = Math.round(MX);
> >         arr[nodeout].rposY = Math.round(MY);
> >         theta += step
> >     }
> > }
> 
> I could have rewritten it with my suggestions incorporated, it's few
> lines of code, but I wouldn't want to spoil the exercise...
> 
> HTH,
> 
> Julio

By the way what do you mean by that the X, Y cordinates not limited to the integer cordinate space. Can computers move pixels slightly by diffuse aspects of them????? I mean the number of pixels is fixed so "WHY" isn't the pixels integer cordinates?

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Thread

Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-08 23:54 -0800
  Re: Refreshing grade school math. "R.Wieser" <address@not.available> - 2020-01-09 09:19 +0100
    Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-09 00:34 -0800
      Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-09 00:43 -0800
        Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-09 00:44 -0800
    Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-11 05:09 -0800
      Re: Refreshing grade school math. Julio Di Egidio <julio@diegidio.name> - 2020-01-11 22:13 -0800
        Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 09:58 -0800
          Re: Refreshing grade school math. Julio Di Egidio <julio@diegidio.name> - 2020-01-13 10:16 -0800
            Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 11:16 -0800
          Re: Refreshing grade school math. "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2020-01-13 12:22 -0800
            Re: Refreshing grade school math. Julio Di Egidio <julio@diegidio.name> - 2020-01-13 12:53 -0800
              Re: Refreshing grade school math. "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2020-01-13 15:31 -0800
              Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 16:03 -0800
            Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 13:00 -0800
              Re: Refreshing grade school math. "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2020-01-13 15:35 -0800
                Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 15:43 -0800
            Re: Refreshing grade school math. Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2020-01-14 01:01 +0100
              Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 16:07 -0800
        Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 10:01 -0800
        Re: Refreshing grade school math. Jonas Thörnvall <jonas.thornvall@gmail.com> - 2020-01-13 10:04 -0800

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