Fix IndexOutOfRangeException when using negative indices in array extensions

[konard]

🐛 Bug Fix

This pull request fixes issue #122 where negative indices passed to array extension methods would cause IndexOutOfRangeException.

📋 Issue Reference

Fixes #122

🔍 Root Cause

The issue was in the GetElementOrDefault and TryGetElement methods in GenericArrayExtensions.cs. The methods only checked:

array != null && array.Length > index

When index < 0, this condition would still be true (since array length is always positive), but accessing array[index] would throw IndexOutOfRangeException.

✅ Solution

Added proper bounds checking by including index >= 0 in all affected methods:

Before:

array != null && array.Length > index

After:

array != null && index >= 0 && array.Length > index

🔧 Methods Fixed

• GetElementOrDefault<T>(this T[] array, int index)
• GetElementOrDefault<T>(this T[] array, long index)
• TryGetElement<T>(this T[] array, int index, out T element)
• TryGetElement<T>(this T[] array, long index, out T element)

🧪 Testing

• Added comprehensive test GetElementWithNegativeIndexTest to verify negative indices behavior
• Added experiment demonstrating the fix works correctly
• All existing tests continue to pass
• Methods now gracefully handle negative indices by returning default values

📊 Test Results

Test Run Successful.
Total tests: 21
     Passed: 21

The fix ensures that:

• Negative indices return default values instead of throwing exceptions
• TryGetElement returns false with default element for negative indices
• All positive valid/invalid indices continue to work as before

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🤖 Generated with Claude Code