Release v2.1.0: Improve overflow handling and add comprehensive tests

- Replace silent infinity returns with explicit OverflowException
- Add overflow detection during calculations
- Expand test coverage with edge cases
- Update documentation for breaking changes
- Bump version to 2.1.0

Author: Nonanti

MathFlow.Core/Combinatorics/CombinatoricsFunctions.cs

@@ -36,7 +36,7 @@ public static double Factorial(double n)
 			throw new ArgumentException("Factorial is only defined for non-negative integers");
 
 		if (n > 170)
-			return double.PositiveInfinity;
+			throw new OverflowException($"Factorial of {n} would overflow. Maximum supported value is 170.");
 
 		double result = 1;
 		for (int i = 2; i <= (int)n; i++)
@@ -53,7 +53,7 @@ public static double Binomial(double n, double k)
 		if (n < 0 || n != Math.Floor(n) || k < 0 || k != Math.Floor(k))
 			throw new ArgumentException("Binomial is only defined for non-negative integers");
 
-		if (n < 0 || k < 0 || k > n)
+		if (k > n)
 			return 0;
 
 		if (k > n - k)
@@ -64,6 +64,9 @@ public static double Binomial(double n, double k)
 		{
 			result *= n - (k - i);
 			result /= i;
+
+			if (double.IsInfinity(result))
+				throw new OverflowException($"Binomial coefficient C({n},{k}) would overflow.");
 		}
 
 		return result;
@@ -79,8 +82,13 @@ public static double Permutation(double n, double k)
 
 		double result = 1;
 		for (int i = 0; i < k; i++)
+		{
 			result *= n - i;
 
+			if (double.IsInfinity(result))
+				throw new OverflowException($"Permutation P({n},{k}) would overflow.");
+		}
+
 		return result;
 	}
 }

MathFlow.Core/MathFlow.Core.csproj

@@ -6,7 +6,7 @@
     <Nullable>enable</Nullable>
     <GeneratePackageOnBuild>false</GeneratePackageOnBuild>
     <PackageId>MathFlow</PackageId>
-    <Version>2.0.0</Version>
+    <Version>2.1.0</Version>
     <Authors>Nonanti</Authors>
     <Description>C# math expression library with symbolic computation support. Parse, evaluate, differentiate, simplify mathematical expressions.</Description>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
@@ -19,7 +19,7 @@
     <PackageReadmeFile>README.md</PackageReadmeFile>
     <PackageIcon>icon.png</PackageIcon>
     <Copyright>Copyright (c) 2025 Nonanti</Copyright>
-    <PackageReleaseNotes>v2.0.0: Complex numbers, enhanced polynomial factoring, new ODE solvers, rational function integration, matrix operations</PackageReleaseNotes>
+    <PackageReleaseNotes>v2.1.0: Added combinatorics functions (binomial, permutation), improved overflow handling, reorganized math functions into CombinatoricsFunctions class</PackageReleaseNotes>
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
     <IncludeSymbols>true</IncludeSymbols>
     <SymbolPackageFormat>snupkg</SymbolPackageFormat>

MathFlow.Tests/CombinatoricsTests.cs

@@ -14,18 +14,43 @@ public CombinatoricsTests()
 	[InlineData("gcd(12, 18)", 6)]
 	[InlineData("lcm(12, 18)", 36)]
 	[InlineData("factorial(5)", 120)]
+	[InlineData("factorial(0)", 1)]
+	[InlineData("factorial(10)", 3628800)]
 	[InlineData("perm(5, 3)", 60)]
 	[InlineData("Permutation(5, 3)", 60)]
 	[InlineData("perm(4, 2)", 12)]
 	[InlineData("perm(6, 0)", 1)]
 	[InlineData("perm(0, 0)", 1)]
 	[InlineData("binomial(5, 3)", 10)]
 	[InlineData("binomial(6, 0)", 1)]
+	[InlineData("binomial(10, 5)", 252)]
 	[InlineData("ncr(6, 6)", 1)]
 	[InlineData("choose(6, 2)", 15)]
 	public void Calculate_CombinatoricsFunctions_ReturnsCorrectResult(string expression, double expected)
 	{
 		var result = _engine.Calculate(expression);
 		Assert.Equal(expected, result, 10);
 	}
+
+	[Theory]
+	[InlineData("factorial(171)")]
+	[InlineData("factorial(200)")]
+	[InlineData("perm(200, 100)")]
+	[InlineData("binomial(1000, 500)")]
+	public void Calculate_LargeNumbers_ThrowsOverflowException(string expression)
+	{
+		Assert.Throws<OverflowException>(() => _engine.Calculate(expression));
+	}
+
+	[Theory]
+	[InlineData("factorial(-1)")]
+	[InlineData("factorial(5.5)")]
+	[InlineData("perm(5, 6)")]
+	[InlineData("perm(-1, 2)")]
+	[InlineData("binomial(5.5, 2)")]
+	[InlineData("binomial(5, -1)")]
+	public void Calculate_InvalidInputs_ThrowsArgumentException(string expression)
+	{
+		Assert.Throws<ArgumentException>(() => _engine.Calculate(expression));
+	}
 }

README.md

@@ -22,7 +22,7 @@ dotnet add package MathFlow
 
 ### Package Reference
 ```xml
-<PackageReference Include="MathFlow" Version="2.0.0" />
+<PackageReference Include="MathFlow" Version="2.1.0" />
 ```
 
 ### Package Manager Console
@@ -46,11 +46,21 @@ var vars = new Dictionary<string, double> { ["x"] = 3, ["y"] = 4 };
 var answer = engine.Calculate("x^2 + y^2", vars); // 25
 ```
 
+## What's New in v2.1.0
+
+### New Features
+- **Combinatorics Functions**: Added binomial coefficients and permutation calculations
+- **Reorganized Math Functions**: GCD, LCM, and factorial moved to dedicated CombinatoricsFunctions class
+
+### Breaking Changes
+- `GCD`, `LCM`, and `Factorial` functions have been moved from their previous location to `CombinatoricsFunctions` class
+- Update your imports if you were using these functions directly
+
 ## What's New in v2.0.0
 
 ### Major Features Added
 - **Complex Number Support**: Full integration with expression parser
-- **Enhanced Polynomial Factoring**: Quadratic, cubic, and special forms  
+- **Enhanced Polynomial Factoring**: Quadratic, cubic, and special forms
 - **New ODE Solvers**: RungeKutta2 and Adams-Bashforth methods
 - **Rational Function Integration**: Partial fractions and special forms
 - **Symbolic Integration**: Extended support for trigonometric and exponential functions