Logical const

[Andrei Alexandrescu]

On 11/30/10 5:25 AM, Max Samukha wrote:
> On 11/30/2010 02:35 AM, Walter Bright wrote:
>> Fawzi Mohamed wrote:
>>> logical const is useful for lazy functions and memoization, and if
>>> implemented correctly it is perfectly safe.
>>> As I said in an older discussions, to have it with the current system
>>> all that is needed is some guarantees that the compiler will not
>>> disallow "unsafe" changes (by moving to read only memory for
>>> example)in some cases.
>>> For example casted mutable types, so that casting to mutable works.
>>
>> D allows escape from the type system, but the programmer who does that
>> loses the guarantees, and it's up to him to ensure that the result works.
>>
>> String literals, for example, are going to often wind up in read only
>> memory.
>
> The problem is that logical const has many perfectly valid use cases.
> You cannot simply tell people: "Don't use it. It is a fraud". They will
> still be using casts or not using D. As casting away const is undefined
> behavior in D, the outcome will be every second non-trivial D program
> relying on undefined behavior.

I'm not seeing half of non-trivial C++ programs using mutable.

Andrei