const by default.

[Dave]

Ok, I know 'const' has been beaten to death in previous threads...

However, one thing that I've not seen beaten to death is 'const by default'.

In the following post, there's a link to comp.lang.c++.moderated where 
Walter puts forward some very good arguments regarding what's wrong with 
C++ (type modifier) const:

http://www.digitalmars.com/drn-bin/wwwnews?digitalmars.D/39437

In that thread, Walter mentions that he should have made const the 
default. Every subsequent post agreed with not one dissenter.

Walter, what exactly do you have in mind? Only reference types? Default 
const for everything? Everything but function local variables? Or 
function return types and function parameters only?

If some type of 'const by default' was implemented, it could have big 
consequences for Phobos. As Phobos is 'officially' supported and 
distributed w/ the compiler, it is the only thing that has to be changed 
along with the compiler.

I'd say:
- add the 'mutable' keyword in v0.163
- let the community start modifying Phobos.
- add a "warn on non-mutable" switch to the compiler by v0.167 (that way 
Walter could implement all of the logic, and later cutover by removing 
the switch and making those errors instead of warnings).
- let the community test Phobos using the new warning switch
- 'cutover' when Phobos is done.

I think the "too much water under the bridge" problem from Walter's 
standpoint is that he can't count on anyone else but himself making the 
changes to Phobos, and he simply doesn't have the time.

I would gladly volunteer for a few of the Phobos modules but I don't 
have the time nor enough explicit knowledge of Phobos to lead the effort 
efficiently. If we could just get the 'mutable' keyword in there, then 
we could start a Dsource project and get "promises" from people in the 
community to do the work.

Just some thoughts on the matter...

Thanks,

- Dave