Const sucks

[Miles]

Walter Bright wrote:
> Const, final, invariant, head const, tail const, it's grown into a
> monster. It tries to cover all the bases, but in doing so is simply not
> understandable.

I was going to say that, that D's const sucks, many months ago, but
didn't because I was afraid being regarded as a troll.

Its not that I like const-less languages like Java (in fact, I hate
them), but I think that C++'s const, with all its problems, was the
right answer (for that time). It fixes the problem without putting much
burden onto the programmer.

D's const puts way too much burden onto the programmer, and gives very
little back. Too many different combinations of const, final, invariant,
pointers and references (and the fact that in D you don't immediately
know if a type "T" is a reference of a value, specially while writing
templates, adds to this confusion) with confusing semantics when
combined (with a few special cases and lack of orthogonality).

When the new const was being designed, I told in this list: "Don't try
to fix what ain't broken". What I meant was: Don't try to do a new const
just because you want a better const than C++s. Many people dislike C++s
const, but are unable to point exactly why it is wrong. Most people
doesn't even understand C++'s const, and try to get more from it than it
was actually intended to provide (that is the whole point behind the new
D's invariant).

Sometimes people give use-cases to exemplify (STL's need for a
difference between iterator<> and const_iterator<> is the first thing
that comes to my mind), but then you ask what a language could provide
to fix this, they don't know. This is where you should aim first you laser.

When I first saw D, I was amazed with the possibilities. Now I'm
somewhat scared. Perhaps one of the things that are scaring me is just
like you said: there is a (at least one) monster in the language.

Just my two cents... I have no interest in trolling anyone.