so what exactly is const supposed to mean?

[Sean Kelly]

Bruno Medeiros wrote:
> Sean Kelly wrote:
>>
>>  > and doesn't D already have a const keyword?
>>
>> D has const as a storage attribute, which is a bit different from the 
>> above.  D's const may only apply to concrete data types, and implies 
>> that the data will never be modified for the duration of the program. 
>> This allows the compiler to place such data in ROM and to perform some 
>> optimizations that would otherwise not be possible.  But this is quite 
>> limited in that it may only be applied to data that can be evaluated 
>> at compile-time.
>>
> 
> There is a slight difference from D's const and a const that places the 
> data in ROM as you cannot get the address of a D const var (it's not an 
> lvalue).

Ever tried taking the address of a const string?  That you can't take 
the address of other const types is simply a result of optimization.

> Resummarizing:
> 
> D's const has two meanings. The usual meaning is from the form:
>   const int var = <some constant initializer>;
> and it means that the variable is a compile-time constant and no storage 
> is allocated for it, instead the value is substituted whenever the var 
> is used (like #define, but safer).
> 
> The second meaning is from the form:
>   const int var; // no initializer
> and means that the var must be initialized once in a constructor, and 
> then it becomes non-recursively immutable (meaning you can't change the 
> value of the var, but you can change referenced values). The var has 
> storage and as such is an lvalue.

Yup.


Sean