Passing array as const slows down code?

[Joseph Rushton Wakeling]

On 27/04/12 20:26, Steven Schveighoffer wrote:
> No, it can't. There can easily be another non-const reference to the same data.
> Pure functions can make more assumptions, based on the types, but it would be a
> very complex determination in the type system to see if two parameters alias the
> same data.
>
> Real optimization benefits come into play when immutable is there.

Question on the const/immutable distinction.  Given that my function has inputs 
of (size_t, size_t, Rating[]), how come the size_t's can be made immutable, but 
the Rating[] can only be made const/const ref?

Is it because the size_t's can't conceivably be changed from outside while the 
function is running, whereas the values in the array in principle can be?