102 lines
3.0 KiB
C#
102 lines
3.0 KiB
C#
using Graphing.Forms;
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using Graphing.Parts;
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namespace Graphing.Graphables;
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public class Equation : Graphable
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{
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private static int equationNum;
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protected readonly EquationDelegate equ;
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protected readonly List<Float2> cache;
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public Equation(EquationDelegate equ)
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{
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equationNum++;
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Name = $"Equation {equationNum}";
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this.equ = equ;
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cache = [];
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}
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public override IEnumerable<IGraphPart> GetItemsToRender(in GraphForm graph)
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{
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const int step = 10;
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double epsilon = Math.Abs(graph.ScreenSpaceToGraphSpace(new Int2(0, 0)).x
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- graph.ScreenSpaceToGraphSpace(new Int2(step / 2, 0)).x) / 5;
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List<IGraphPart> lines = [];
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double previousX = graph.MinVisibleGraph.x;
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double previousY = GetFromCache(previousX, epsilon);
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for (int i = 1; i < graph.ClientRectangle.Width; i += step)
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{
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double currentX = graph.ScreenSpaceToGraphSpace(new Int2(i, 0)).x;
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double currentY = GetFromCache(currentX, epsilon);
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if (Math.Abs(currentY - previousY) <= 10)
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{
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lines.Add(new GraphLine(new Float2(previousX, previousY), new Float2(currentX, currentY)));
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}
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previousX = currentX;
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previousY = currentY;
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}
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return lines;
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}
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public EquationDelegate GetDelegate() => equ;
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public override void EraseCache() => cache.Clear();
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protected double GetFromCache(double x, double epsilon)
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{
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(double dist, double nearest, int index) = NearestCachedPoint(x);
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if (dist < epsilon) return nearest;
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else
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{
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double result = equ(x);
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cache.Insert(index + 1, new(x, result));
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return result;
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}
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}
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// Pretty sure this works. Certainly works pretty well with "hard-to-compute"
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// equations.
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protected (double dist, double y, int index) NearestCachedPoint(double x)
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{
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if (cache.Count == 0) return (double.PositiveInfinity, double.NaN, -1);
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else if (cache.Count == 1)
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{
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Float2 single = cache[0];
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return (Math.Abs(single.x - x), single.y, 0);
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}
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else
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{
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int boundA = 0, boundB = cache.Count;
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do
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{
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int boundC = (boundA + boundB) / 2;
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Float2 pointC = cache[boundC];
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if (pointC.x == x) return (0, pointC.y, boundC);
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else if (pointC.x > x)
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{
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boundA = boundC;
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}
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else // pointC.x < x
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{
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boundB = boundC;
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}
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} while (boundB - boundA > 1);
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return (Math.Abs(cache[boundA].x - x), cache[boundA].y, boundA);
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}
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}
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public override Graphable DeepCopy() => new Equation(equ);
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public override long GetCacheBytes() => cache.Count * 16;
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}
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public delegate double EquationDelegate(double x);
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