> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # C# Range The `..` (range) operator constructs a `System.Range` struct that represents a contiguous sub-segment of a collection. It serves as syntactic sugar for defining boundaries, utilizing `System.Index` types to specify an inclusive lower bound and an exclusive upper bound. ## Syntax and Operands The operator accepts two optional operands. Because both operands are optional, the operator supports four distinct syntax variations: * **Left operand:** The inclusive start index. If omitted, it defaults to `0` (the beginning of the collection). * **Right operand:** The exclusive end index. If omitted, it defaults to `^0` (the end of the collection). ```csharp theme={"dark"} Range explicitBounds = 2..5; // Index 2 (inclusive) to Index 5 (exclusive) Range openEnd = 2..; // Index 2 (inclusive) to the end of the collection Range openStart = ..5; // Beginning of the collection to Index 5 (exclusive) Range openBoth = ..; // The entire collection (0 to ^0) ``` ## Type Resolution and Compilation Operands supplied to the `..` operator must evaluate to type `int` or `System.Index`. When standard integers are provided, the compiler implicitly converts them to `System.Index` structs. During compilation, the `..` syntax is lowered directly into an instantiation of the `System.Range` struct via its constructor. ```csharp theme={"dark"} // Source syntax using the range operator (..) and index from end operator (^) Range range = 1..^1; // Lowered compiler translation Index start = new Index(value: 1, fromEnd: false); Index end = new Index(value: 1, fromEnd: true); Range loweredRange = new Range(start, end); ``` ## Operator Characteristics * **Associativity:** The `..` operator is non-associative. Chaining the operator (e.g., `a..b..c`) is syntactically invalid and produces a compiler error. * **Precedence:** It evaluates with lower precedence than arithmetic operators (like `+` or `*`) but higher precedence than relational and equality operators (like `<` or `==`). * **Immutability:** The `System.Range` struct generated by the operator is a `readonly struct`. Its `Start` and `End` properties cannot be mutated after initialization.
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