Question

I can declare foo(const T& var) so that I know var won’t be changed.

Equivalent format for pointer would be foo(const T* var)?

In the past I tried those, errors related to iterator/const_iterator irritated me and I just tended to use (T* var) without considering constness.

Are there a good doc for declaring function that enforces contents pointed by a pointer won’t change’?

Answer 1

What you have is already a pointer that prohibits the pointee’s contents from changing. You can see this by using the “read backwards” rule:

const T* var     <===== left to right from this read

Reading backwards:

var is a pointer to a T that is constant

This is different from

T* const var

Which reads:

var is a constant pointer to a T

The difference here is that the constant is var, not the T; that means you can change the T by dereferencing var but you cannot change what var points to.

And of course you can have both of the above at the same time:

const T* const var