I'm writing a collection with functionality for membership checking. I thought it would be nice to use the "in" operator. In the docs for std.collections I surmise that this is the standard way to go. From the source code, I see there's no special opIn, but that it can be done with the more general...

   bool opBinary(string op)(T k) if (op == "in") {
       ...
   }

Here T is, of course, a compile-time argument of the surrounding struct or class.

So ... this is used in the the Phobos source in the DMD 2.052 distro (if I'm not mistaken), but I can't get dmd 2.052 to accept it? I keep getting the error message "Error: rvalue of in expression must be an associative array, not Foo!(uint)".

I guess either that this is a recent feature -- I didn't see it mentioned in Andrei's book -- and that my Phobos source is too recent for my dmd ... or that I'm doing something wrong elsewhere in my code, preventing the operator overloading to take force. Suggestions/solutions?-)

-- 
Magnus Lie Hetland
http://hetland.org

Am 04.03.2011 17:01, schrieb Magnus Lie Hetland:
> I'm writing a collection with functionality for membership checking. I
> thought it would be nice to use the "in" operator. In the docs for
> std.collections I surmise that this is the standard way to go. From the
> source code, I see there's no special opIn, but that it can be done with
> the more general...
>
> bool opBinary(string op)(T k) if (op == "in") {
> ...
> }
>
> Here T is, of course, a compile-time argument of the surrounding struct
> or class.
>
> So ... this is used in the the Phobos source in the DMD 2.052 distro (if
> I'm not mistaken), but I can't get dmd 2.052 to accept it? I keep
> getting the error message "Error: rvalue of in expression must be an
> associative array, not Foo!(uint)".
>
> I guess either that this is a recent feature -- I didn't see it
> mentioned in Andrei's book -- and that my Phobos source is too recent
> for my dmd ... or that I'm doing something wrong elsewhere in my code,
> preventing the operator overloading to take force. Suggestions/solutions?-)
>

If you try to use it in the manner of `something in classWhichDefinesThisOpBinary` then it doesn't work because operator overloading normally overloads on the left operand (ie something). Use opBinaryRight(string op)(...) if(...) to get it working.

Mafi

On 2011-03-04 17:06:29 +0100, Mafi said:

> If you try to use it in the manner of `something in classWhichDefinesThisOpBinary` then it doesn't work because operator overloading normally overloads on the left operand (ie something). Use opBinaryRight(string op)(...) if(...) to get it working.

Aaah. That makes sense. And works.

*But*: I copied my code from Phobos :D If you search for "in", with the quotes, in std/container.d, you'll find two occurrences. The actual live use (in RedBlackTree) is opBinaryRight (which makes sense), but in the dummy class, TotalContainer, which is described as "an unimplemented container that illustrates a host of primitives that a container may define", uses just opBinary. The doc-comment says that "$(D k in container) returns true if the given key is in the container".

So ... a "bug", I guess? (One that isn't really executed -- but still...) Worth reporting?

Anwyay: Thanks for the clarification :)

-- 
Magnus Lie Hetland
http://hetland.org

Magnus Lie Hetland <magnus@hetland.org> wrote:

> On 2011-03-04 17:06:29 +0100, Mafi said:
>
>> If you try to use it in the manner of `something in classWhichDefinesThisOpBinary` then it doesn't work because operator overloading normally overloads on the left operand (ie something). Use opBinaryRight(string op)(...) if(...) to get it working.
>
> Aaah. That makes sense. And works.
>
> *But*: I copied my code from Phobos :D If you search for "in", with the quotes, in std/container.d, you'll find two occurrences. The actual live use (in RedBlackTree) is opBinaryRight (which makes sense), but in the dummy class, TotalContainer, which is described as "an unimplemented container that illustrates a host of primitives that a container may define", uses just opBinary. The doc-comment says that "$(D k in container) returns true if the given key is in the container".
>
> So ... a "bug", I guess? (One that isn't really executed -- but still...) Worth reporting?
>
> Anwyay: Thanks for the clarification :)

Definitely report it.


-- 
Simen

On 03/04/2011 05:01 PM, Magnus Lie Hetland wrote:
> I'm writing a collection with functionality for membership checking. I thought
> it would be nice to use the "in" operator. In the docs for std.collections I
> surmise that this is the standard way to go. From the source code, I see
> there's no special opIn, but that it can be done with the more general...
>
> bool opBinary(string op)(T k) if (op == "in") {
> ...
> }
>
> Here T is, of course, a compile-time argument of the surrounding struct or class.
>
> So ... this is used in the the Phobos source in the DMD 2.052 distro (if I'm
> not mistaken), but I can't get dmd 2.052 to accept it? I keep getting the error
> message "Error: rvalue of in expression must be an associative array, not
> Foo!(uint)".
>
> I guess either that this is a recent feature -- I didn't see it mentioned in
> Andrei's book -- and that my Phobos source is too recent for my dmd ... or that
> I'm doing something wrong elsewhere in my code, preventing the operator
> overloading to take force. Suggestions/solutions?-)

Didn't even know 'in' can be defined with opBinary...
I use opIn_r ('r' for right side, since the container stand on the right of the expression) everywhere, and it works fine.

Denis
-- 
_________________
vita es estrany
spir.wikidot.com

On 2011-03-04 18:08:08 +0100, spir said:

> Didn't even know 'in' can be defined with opBinary...
> I use opIn_r ('r' for right side, since the container stand on the right of the expression) everywhere, and it works fine.

Huh. Cool. Works like a charm. Seems cleaner like the opBinaryRight solution, really. I just didn't know of it :)

-- 
Magnus Lie Hetland
http://hetland.org

On 03/04/2011 10:41 AM, Magnus Lie Hetland wrote:
> On 2011-03-04 18:08:08 +0100, spir said:
>
>> Didn't even know 'in' can be defined with opBinary...
>> I use opIn_r ('r' for right side, since the container stand on the
>> right of the expression) everywhere, and it works fine.
>
> Huh. Cool. Works like a charm. Seems cleaner like the opBinaryRight
> solution, really. I just didn't know of it :)
>

It can be seen on the D1 documentation:

  http://www.digitalmars.com/d/1.0/operatoroverloading.html

That is (or "will be") deprecated in D2.

Ali