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digitalmars.D.learn - How can I save a class use the RedBlackTree?

reply Dsby <dushibaiyu yahoo.com> writes:
this is the test Code:


import std.container.rbtree;
import std.stdio;

class TClass
{
     int i;
}

void main()
{
     RedBlackTree!(TClass) list = new RedBlackTree!(TClass)();
     auto t = new TClass();
     list.insert(t);
     writeln("The rbtree length is ",list.length());
     list.removeKey(t);
     writeln("The rbtree length is ",list.length());
}

and thisis erro :
/usr/include/dlang/dmd-2.071.0/phobos/std/functional.d-mixin-206(206): Error:
mutable method object.Object.opCmp is not callable using a inout object
/usr/include/dlang/dmd-2.071.0/phobos/std/container/rbtree.d(871): Error:
template instance std.functional.binaryFun!("a < b", "a",
"b").binaryFun!(inout(TClass), TClass) error instantiating
rbtree.d(11):        instantiated from here: 
RedBlackTree!(TClass, "a < b", false)
/usr/include/dlang/dmd-2.071.0/phobos/std/functional.d-mixin-206(206): Error:
function object.Object.opCmp (Object o) is not callable using argument types
(inout(TClass))
/usr/include/dlang/dmd-2.071.0/phobos/std/container/rbtree.d(873): Error:
template instance std.functional.binaryFun!("a < b", "a",
"b").binaryFun!(TClass, inout(TClass)) error instantiating
rbtree.d(11):        instantiated from here: 
RedBlackTree!(TClass, "a < b", false)
May 02 2016
parent reply Steven Schveighoffer <schveiguy yahoo.com> writes:
On 5/3/16 5:10 AM, Dsby wrote:

 this is the test Code:


 import std.container.rbtree;
 import std.stdio;

 class TClass
 {
      int i;
 }

 void main()
 {
      RedBlackTree!(TClass) list = new RedBlackTree!(TClass)();
      auto t = new TClass();
      list.insert(t);
      writeln("The rbtree length is ",list.length());
      list.removeKey(t);
      writeln("The rbtree length is ",list.length());
 }

 and thisis erro :
 /usr/include/dlang/dmd-2.071.0/phobos/std/functional.d-mixin-206(206):
 Error: mutable method object.Object.opCmp is not callable using a inout
 object
 /usr/include/dlang/dmd-2.071.0/phobos/std/container/rbtree.d(871):
 Error: template instance std.functional.binaryFun!("a < b", "a",
 "b").binaryFun!(inout(TClass), TClass) error instantiating
 rbtree.d(11):        instantiated from here: RedBlackTree!(TClass, "a <
 b", false)
 /usr/include/dlang/dmd-2.071.0/phobos/std/functional.d-mixin-206(206):
 Error: function object.Object.opCmp (Object o) is not callable using
 argument types (inout(TClass))
 /usr/include/dlang/dmd-2.071.0/phobos/std/container/rbtree.d(873):
 Error: template instance std.functional.binaryFun!("a < b", "a",
 "b").binaryFun!(TClass, inout(TClass)) error instantiating
 rbtree.d(11):        instantiated from here: RedBlackTree!(TClass, "a <
 b", false)



bleh, Object.opCmp only works with mutable objects. Which means 
RedBlackTree cannot work with objects because it uses inout to ensure 
your objects are not modified (since 2.068)

It doesn't work with const or immutable either, the only possible 
solution is to go back to mutable only.

So annoying, we need to fix Object.opCmp, or using const/immutable 
comparisons with objects doesn't work.

-Steve
May 03 2016
parent reply Jonathan M Davis via Digitalmars-d-learn writes:
On Tue, 3 May 2016 11:37:13 +0200
Steven Schveighoffer via Digitalmars-d-learn
<digitalmars-d-learn puremagic.com> wrote:

 bleh, Object.opCmp only works with mutable objects. Which means
 RedBlackTree cannot work with objects because it uses inout to ensure
 your objects are not modified (since 2.068)

 It doesn't work with const or immutable either, the only possible
 solution is to go back to mutable only.

 So annoying, we need to fix Object.opCmp, or using const/immutable
 comparisons with objects doesn't work.


Hopefully someday...

https://issues.dlang.org/show_bug.cgi?id=9770

- Jonathan M Davis
May 03 2016
parent reply Meta <jared771 gmail.com> writes:
On Tuesday, 3 May 2016 at 12:12:04 UTC, Jonathan M Davis wrote:

 On Tue, 3 May 2016 11:37:13 +0200
 Steven Schveighoffer via Digitalmars-d-learn
 <digitalmars-d-learn puremagic.com> wrote:

 bleh, Object.opCmp only works with mutable objects. Which 
 means RedBlackTree cannot work with objects because it uses 
 inout to ensure your objects are not modified (since 2.068)

 It doesn't work with const or immutable either, the only 
 possible solution is to go back to mutable only.

 So annoying, we need to fix Object.opCmp, or using 
 const/immutable comparisons with objects doesn't work.


 Hopefully someday...

 https://issues.dlang.org/show_bug.cgi?id=9770

 - Jonathan M Davis


What's stopping us right now from making opCmp a free function in 
object.d?
May 03 2016
parent Jonathan M Davis via Digitalmars-d-learn writes:
On Tuesday, May 03, 2016 13:26:22 Meta via Digitalmars-d-learn wrote:

 On Tuesday, 3 May 2016 at 12:12:04 UTC, Jonathan M Davis wrote:

 On Tue, 3 May 2016 11:37:13 +0200
 Steven Schveighoffer via Digitalmars-d-learn

 <digitalmars-d-learn puremagic.com> wrote:

 bleh, Object.opCmp only works with mutable objects. Which
 means RedBlackTree cannot work with objects because it uses
 inout to ensure your objects are not modified (since 2.068)

 It doesn't work with const or immutable either, the only
 possible solution is to go back to mutable only.

 So annoying, we need to fix Object.opCmp, or using
 const/immutable comparisons with objects doesn't work.


 Hopefully someday...

 https://issues.dlang.org/show_bug.cgi?id=9770

 - Jonathan M Davis


 What's stopping us right now from making opCmp a free function in
 object.d?


In general, the two big blockers for removing opEquals, opCmp, toString, and
toHash from Object are

1. The built-in AAs either need to be fixed so that they don't need Object
and use the actual type that you're telling them to use (e.g. by
templatizing them internally), or using classes as keys in the built-in AAs
needs to be deprecated. The first requires fixing the built-in AAs, which is
a huge pain. There have been several attempts, but AFAIK, no one has ever
succeeded (Martin was the last one to try from what I recall, but I don't
know how far he got). The second requires that we have a proper replacement
in Phobos so that folks would actually have an alternative when using
classes as keys was deprecated. At some point here, we're going to need to
decide whether it's actually feasible to fix the built-in AAs, or whether we
should just reduce what they can do to the sane subset, but it doesn't
necessarily matter much as long as we don't have a viable HashMap/HashTable
implementation in Phobos.

2. One or more compiler devs have to be convinced to prioritize making the
changes required to actually deprecate these functions without breaking code
(which isn't exactly straightforward). And we haven't even worked out yet
exactly how such deprecations would work. It would be trivial if we could
just break code, and the changes required in programmers are likely to be
minor, but immediately breaking code like that without a deprecation path is
not acceptable.

As for making opCmp a free function, that's not how operator overloading
works. The fact that opEquals ends up using a free function to call the
opEquals on your type is an anomally (it's required for opEquals because of
communutativity concerns). It _might_ make sense for opCmp for the same
reasons but only if opCmp is required to have strict ordering (which is a
matter of some debate).  But even if it did make sense to turn opCmp into a
free function, making that work rather than just creating a free function
called opCmp that never gets used by anything would likely require effort
similar to (or worse than) what would be required to make it possible to
cleanly deprecate opCmp on Object.

The first concern is sorting out what we do with the built-in AAs, which is
potentially blocked by Andrei's revamping of std.container so that we can
have a proper HashMap/HashTable in Phobos. The second concern is then
figuring out the best way to go about actually deprecating those 4 functions
and getting someone to do it. I expect that it will happen, but it's blocked
by some stuff that could take a while, and it hasn't been a high priority.

- Jonathan M Davis
May 08 2016