23.1 The 3 ways of passing a value

When passing a value to a function, Rust proposes three possibilities:

• Passing by value: this is done implicitly, when the value’s type implements the Copy trait (e.g.: integers, floats, ...).

• Passing by ownership: this is done implicitly, when a value’s type does not implement the Copy type. The ownership of the value is passed to the function. The caller has the choice to make a clone if the value’s type implements the Clone trait, in which case the clone’s ownership will be passed to the function instead of the original value’s.

• Passing by reference: this is done explicitly by both the caller and the function. The caller keeps the ownership of the value, and the function borrows the value.