On 05/13/2012 06:39 PM, Stewart Gordon wrote:
http://d.puremagic.com/issues/show_bug.cgi?id=1824
This has gone on for too long.
Object.toString, .toHash, .opCmp and .opEquals should all be const.
No, please.
Transitive enforced const + OO -> epic fail. (especially for unshared
data, which is the default and most common)
The lack of head-mutable class references does not make this any better.
I'd rather keep the current state of affairs than blindly mark the
existing methods const. Caching/lazy evaluation is everywhere. One
single lazily cached class member implies that all of the relevant
methods cannot use that member. What if they have to? They certainly
have to!
Const/immutable are great for simple value-types. Classes can contain
immutable values as fields.
(It's also been stated somewhere that they should be pure and nothrow,
or something like that, but I forget where.)
Similar concerns apply for them (but less so than for const). I don't
want to have to violate the type system to get basic stuff done in
OO-ish style! Forced const invariants are annoying enough already.
This makes it a nightmare to use const objects in data structures,
Why on earth would you want to do that?
among other things, at best forcing the use of ugly workarounds. There are
probably other, more serious effects of this that can't easily be worked
around.
I wouldn't bet on that. Marking the methods const, on the other hand,
certainly would have serious effects.
It seems that the main obstacle is rewriting the relevant methods in
std.stream. The current implementation doesn't make sense anyway -
reading the entire contents of a file is certainly not the way to
generate a hash or string representation of the stream. I'm thinking the
hash should probably be the stream handle, and the string representation
could perhaps be the full pathname of the file. Of course, what it
should be for non-file streams is another matter. (This would be a
change at the API level, but when the API's as fundamentally flawed as
this....)
Are there any other bits of druntime/Phobos that need to be sorted out
before these methods can be declared const/pure/nothrow once and for all?
Almost _all_ of Phobos would have to become const "correct", and it
cannot, because 'const' is an over-approximation and there is no
const-inference. const on the top-class interface invades _everything_.
Marking the methods const would break every non-trivial D program out
there and put programmers in a frustrating straitjacket.
