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A multi-line comment in Swift is a lexical construct that instructs the compiler to ignore a specific block of text spanning one or more lines during the tokenization phase. It is defined using a forward-slash followed by an asterisk (/*) as the opening delimiter, and an asterisk followed by a forward-slash (*/) as the closing delimiter. Any characters placed between these delimiters are treated as whitespace by the Swift compiler. 
/*
This is a standard multi-line comment.
The Swift compiler will completely ignore
everything between the opening and closing delimiters.
*/
Unlike many C-family languages, Swift supports nested multi-line comments. The compiler tracks the depth of the comment blocks, requiring every opening delimiter (/*) to be matched with a corresponding closing delimiter (*/) before the standard parsing of source code resumes. 
/*
Outer multi-line comment block initiated.

    /*
    Inner nested multi-line comment block.
    The compiler increments the nesting depth here.
    */

The compiler decrements the nesting depth above, 
but continues ignoring text until the outer block is closed.
*/
Because the compiler evaluates the nesting depth, an inner */ will not prematurely terminate the outer /*. The lexical analyzer will only resume standard token generation once the nesting depth returns to zero.
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