In a functional language like Clojure, it should not possible to permanently (or globally) modify the contents of a data structure that has been passed into a function as a parameter.
So, with a vector parameter for example, which of the following approaches is used by the Clojure environment to ensure that accidental modifications do no occur?

Question

In a functional language like Clojure, it should not possible to permanently (or globally) modify the contents of a data structure that has been passed into a function as a parameter.  
 So, with a vector parameter for example, which of the following approaches is used by the Clojure environment to ensure that accidental modifications do no occur?

Accepted Answer

A new index path is created only for those values in the vector that are modified

Answer

A copy of the vector is created, thereby ensuring that modifications can not affect the calling function.

Answer

You can not pass a vector directly, as the programmer must create a copy first and pass the copy to the new function.

Answer

A new complete index is created when the vector is passed into the function, but the vector itself remains the same so that it does not have to be copied.

Answer

Only scalar/primitive values can be passed as parameters in functional languages, as it is too expensive to make copies of large objects like vectors.

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In a functional language like Clojure, it should not possible to permanently (or...

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