How do Variadic Functions Work in Go: Unpacking the '...' Syntax?

Variadic Functions in Go: Understanding "...Type"

The Go language allows you to define functions with variable-length argument lists, known as variadic functions. The syntax of a variadic function is to append an ellipsis (...) to the last parameter type.

Syntax:

func functionName(param1, param2, ..., paramN ...Type)

where:

• paramN is the name of the variadic parameter.
• Type is the type of the variadic parameter.
• The ellipsis indicates that the parameter can accept zero or more arguments of the specified type.

Example:

The code from builtin.go serves as documentation, not compiled code. The line:

func append(slice []Type, elems ...Type) []Type

demonstrates a variadic function called append. This function can accept two or more parameters: the first is a slice of type []Type, and the second is a variadic parameter that can accept any number of elements of type Type.

Usage:

In your code, you can call the append function with the same syntax as any other function:

s3 := append(s1, s2...)

In this example, the append function concatenates the two slices s1 and s2, which results in the new slice s3. The ellipsis used with s2 indicates that all elements of s2 should be copied into s3.

Additional Notes:

• Variadic functions can only have one variadic parameter, which must be the last parameter in the function signature.
• The type of the variadic parameter can be any Go type, including structs and interfaces.
• Variadic functions are often used to provide flexibility when a function can accept an arbitrary number of arguments.

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