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Free Functions vs. Associated Functions (Methods)#

Feature	Free Function	Associated Function (Method)
Definition	Defined at the module level, not within an `impl` block.	Defined within an impl block for a struct or a trait.
Calling Syntax	`function_name(args)` or `module::function_name(args)`.	`instance.method_name(args)` or `Struct::method_name(args)` (if it doesn’t take `&self`, `&mut self`, or `self`).
`self` Parameter	Does not take `&self`, `&mut self`, or `self` as a parameter.	Takes `&self`, `&mut self`, or `self` to operate on an instance of the struct.
Use Case	Often used for static utility functions, operations where no single data “owner” is clear, or generic functions.	Used when the function’s logic is tightly coupled to a specific data structure.