Is my understanding below correct? Does any documentation need updating?

Operator precedence table lists !in as an operator:

  http://wiki.dlang.org/Operator_precedence

Operator overloading documentation does not mention it:

  http://dlang.org/operatoroverloading.html#binary

However, 'a !in b' seems to be lowered to '!(a in b)'. It is possible to define "!in" but it is never called:

struct S
{
    bool opBinaryRight(string op)(int i) const
        if (op == "in")
    {
        import std.stdio;
        writeln("in");
        return true;
    }

    bool opBinaryRight(string op)(int i) const
        if (op == "!in")
    {
        // Never called
        assert(false);
        return false;
    }
}

void main()
{
    auto s = S();
    assert(42 in s);
    assert(!(42 !in s));
}

The "in" overload gets called twice:

in
in

Ali

On Sunday, August 02, 2015 21:51:48 Ali Çehreli via Digitalmars-d-learn wrote:
> Is my understanding below correct? Does any documentation need updating?
>
> Operator precedence table lists !in as an operator:
>
>    http://wiki.dlang.org/Operator_precedence
>
> Operator overloading documentation does not mention it:
>
>    http://dlang.org/operatoroverloading.html#binary
>
> However, 'a !in b' seems to be lowered to '!(a in b)'. It is possible to define "!in" but it is never called:
>
> struct S
> {
>      bool opBinaryRight(string op)(int i) const
>          if (op == "in")
>      {
>          import std.stdio;
>          writeln("in");
>          return true;
>      }
>
>      bool opBinaryRight(string op)(int i) const
>          if (op == "!in")
>      {
>          // Never called
>          assert(false);
>          return false;
>      }
> }
>
> void main()
> {
>      auto s = S();
>      assert(42 in s);
>      assert(!(42 !in s));
> }
>
> The "in" overload gets called twice:
>
> in
> in

It would make no sense to be able to overload !in directly given D's philosophy on operator overloading. key !in foo has to be the same as !(key in foo) for consistency. It's the same as why opEquals, opCmp, op!"++", and op!"--" are all used to overload multiple operators.

- Jonathan M Davis