D - more or less power than C++?

[Johan Granberg]

Ben Phillips wrote:
> In article <dubpge$u3r$1 at digitaldaemon.com>, Johan Granberg says...
>>>> 1. const parameters and member functions
>>>>
>>>> Countless times this saved me. I just can't imagine references being
>>>> passed in and out of functions without something explicitly saying that
>>>> the function is expected or not to modify it.
>> You did not answer the above statement and i have seen this repeated all 
>> over this thread along with destructors in structs.
>>
> 
> A method can explicitly say that it will modify a reference by using "out" and
> "inout".
> 
> I've never cared much for const member methods, so I'm confused as to how a lack
> of them can cause such a problem. Can you give an example?
> 
> 
It is not const methods so much as const in parameters.

class A
{
  int bar=1;//bar should bee read only
}

void foo(in i a)//I want a to bee readonly
{
     i.bar=2;//here the value should not be writable but since a is
             //a reference it is
}

A a=new A;//bar is 1
foo(a);
print(a.bar);//prints 2

It is not so very usefull in smal examples but if you have a large 
program and do that by mistake it could cause a bug. Basicaly it is a 
message from the writer of a class to it's users of how member are to 
bee used, and aditionaly it has compiler suport to catch typos and 
mistakes, if a user realy want to change the data against the orginal 
authors recomendations he can use a explicit cast.