Add Bestdori chart converter.

Assets/Cryville/Common/Math/FractionUtils.cs

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+using System;
+
+namespace Cryville.Common.Math {
+	/// <summary>
+	/// Provides a set of <see langword="static" /> methods related to fractions.
+	/// </summary>
+	public static class FractionUtils {
+		/// <summary>
+		/// Converts a <see cref="double" /> decimal to a fraction.
+		/// </summary>
+		/// <param name="value">The decimal.</param>
+		/// <param name="error">The error.</param>
+		/// <param name="n">The numerator.</param>
+		/// <param name="d">The denominator.</param>
+		/// <exception cref="ArgumentOutOfRangeException"><paramref name="value" /> is less than 0 or <paramref name="error" /> is not greater than 0 or not less than 1.</exception>
+		public static void ToFraction(double value, double error, out int n, out int d) {
+			if (value < 0.0)
+				throw new ArgumentOutOfRangeException("value", "Must be >= 0.");
+			if (error <= 0.0 || error >= 1.0)
+				throw new ArgumentOutOfRangeException("accuracy", "Must be > 0 and < 1.");
+
+			int num = (int)System.Math.Floor(value);
+			value -= num;
+
+			if (value < error) { n = num; d = 1; return; }
+			if (1 - error < value) { n = num + 1; d = 1; return; }
+
+			int lower_n = 0;
+			int lower_d = 1;
+			int upper_n = 1;
+			int upper_d = 1;
+			while (true) {
+				int middle_n = lower_n + upper_n;
+				int middle_d = lower_d + upper_d;
+
+				if (middle_d * (value + error) < middle_n) {
+					upper_n = middle_n;
+					upper_d = middle_d;
+				}
+				else if (middle_n < (value - error) * middle_d) {
+					lower_n = middle_n;
+					lower_d = middle_d;
+				}
+				else {
+					n = num * middle_d + middle_n;
+					d = middle_d;
+					return;
+				}
+			}
+		}
+	}
+}

Assets/Cryville/Common/Math/FractionUtils.cs.meta

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