FAQ 14.10 When should const not be used in declaring formal parameters?

FAQ 14.10 When should const not be used in declaring formal parameters?

Do not use const for formal parameter types that are passed by value, because a const on a pass-by-value parameter affects (constrains) only the code inside the function; it does not affect the caller. For example, replace f(const Fred x) with either f(const Fred& x) or f(Fred x).

As a special case of this rule, it is inappropriate to use Fred* const in a formal parameter list. For example, replace f(Fred* const p) with f(Fred* p), and replace g(const Fred* const p) with g(const Fred* p).

Finally, do not use Fred& const in any context. The construct is nonsensical because a reference can never be rebound to a different object. (See FAQ 14.01.)