C# Logical XOR - SyntBlaze

The ^ operator in C# serves two distinct syntactic roles depending on its context: as a binary Logical/Bitwise Exclusive OR (XOR) operator, and as a unary Index from End operator.

1. Logical and Bitwise Exclusive OR (XOR) Operator

When used as a binary operator between two operands, ^ computes the exclusive OR. The evaluation mechanics depend strictly on the operand types:

Boolean Operands (bool): Performs a logical XOR. It evaluates to true if and only if exactly one operand is true. If both operands share the same boolean value, it evaluates to false.
Integral Operands (int, uint, long, etc.): Performs a bitwise XOR. It compares the binary representations of the operands bit by bit, resulting in 1 where the corresponding bits differ, and 0 where they match.

// Logical XOR
bool logicalResult1 = true ^ false; // Evaluates to true
bool logicalResult2 = true ^ true;  // Evaluates to false

// Bitwise XOR
int bitwiseResult = 5 ^ 3;          // Evaluates to 6
/* Bitwise evaluation:
   0101 (5 in binary)
 ^ 0011 (3 in binary)

   0110 (6 in binary)
*/

The binary ^ operator also supports compound assignment via ^=, which applies the XOR operation and assigns the result to the left operand.

int value = 5;
value ^= 3; // Equivalent to: value = value ^ 3; (Evaluates to 6)

2. Index from End Operator

Introduced in C# 8.0, when used as a unary prefix operator, ^ instantiates a System.Index struct. It specifies an index relative to the end of a sequence (such as an array, Span<T>, or string), rather than the beginning. The index ^n translates to sequence.Length - n at runtime. Consequently, ^1 points to the last element in the sequence. ^0 points to the sequence length itself; while ^0 throws an IndexOutOfRangeException if used for direct element access, it is syntactically valid and required when defining an exclusive upper bound in a System.Range.

int[] numbers = { 10, 20, 30, 40, 50 };

// Direct indexing
int last = numbers[^1];         // Evaluates to 50 (numbers.Length - 1)
int secondToLast = numbers[^2]; // Evaluates to 40 (numbers.Length - 2)

// Range indexing (..) using Index from End
// Extracts from index 1 up to, but not including, the last element
int[] slice = numbers[1..^1];   // Evaluates to { 20, 30, 40 }

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​1. Logical and Bitwise Exclusive OR (XOR) Operator

​2. Index from End Operator

1. Logical and Bitwise Exclusive OR (XOR) Operator

2. Index from End Operator