readonly storage class

[Timon Gehr]

On 04/08/2012 11:16 AM, Benjamin Thaut wrote:
> While typing D code I usually come across the problem that neither const
> nor immutable describe the usage pattern of the memory I'm currently
> working on 100%. Sometimes I have immutable data that has been shared
> among threads that I want to pass to a function. Then I have some const
> data that I want to pass to the same function. Currently you don't have
> any other choice but to write that function two times. But the function
> itself does not need the "extended" properties of const or immutable:
>
> const: can be casted back to mutable

It cannot.

> immutable: can be implicitly shared among threads
>
> The only thing the function cares about is, that it will not change the
> data passed to it. It would be kind of nice to have a thrid storage
> class "readonly". It can not be casted back to mutable and it can not be
> implicitly shared among threads, but both const and immutable implicitly
> convert to readonly, because both of these storage classes lose one of
> their properties during conversion. That way you only have to write the
> function once and can pass both const and immutable data to it.
>
> Just an idea, comments and critics welcome.
>

I don't get the problem. Can you demonstrate the issue with an example?