Stick a fork in it

[janderson]

Bill Baxter wrote:
> Chris Miller wrote:
>> On Wed, 09 May 2007 14:56:14 -0400, Walter Bright 
>> <newshound1 at digitalmars.com> wrote:
>>
>>> I'm currently working on implementing const/invariant. It's becoming 
>>> clear that this is a pervasive change, and will cause binary 
>>> incompatibility with existing code. I'm trying to minimize any source 
>>> incompatibilities.
>>>
>>> The first few iterations of const support probably will have lots of 
>>> problems before it gets usable.
>>>
>>> This means that dmd will have to fork into a 1.x maintenance version 
>>> and a 2.x beta.
>>
>>
>> Well, hooray...
>>
>> But I wonder about this const stuff. I remember a song similar to 
>> "here a const, there a final, everywhere an invariant final" ;)
> 
> 
> That't the observation that leads one to start thinking about making 
> const the default in places where it makes sense.  Like on reference 
> parameters to functions.  Rather than having to explicitly declare "hey 
> I'm not going to modify this data" you only have to explicitly declare 
> the "hey I AM going to modify this data" case.
> 
> I really don't know if it would end up being a net gain.  But it seems 
> appealing.  The nice thing is that with C++ const arguments, if you 
> write a function foo() that doesn't modify its arguments, but forget to 
> mark the args as const, it's often some OTHER programmer who discovers 
> that fact, because you might never try to call foo with a const param in 
> your program.  But the poor other programmer who discovers it has to 
> figure out whether to modify your code, or try to get you to fix it, or 
> submit a patch or whatever, or const cast.
> 
> But with const default, if you forget to specify foo's arguments as 
> mutable and you start trying to modify them in the function you're going 
> to find out right away, when you're writing foo, not some time later 
> when you try to call foo.
> 
> --bb

I think that's a good idea.