http://d.puremagic.com/issues/show_bug.cgi?id=7520

           Summary: opDollar undocumented
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: websites
        AssignedTo: nobody@puremagic.com
        ReportedBy: robert@octarineparrot.com


--- Comment #0 from Robert Clipsham <robert@octarineparrot.com> 2012-02-16 15:34:02 GMT ---
There does not appear to be any documentation for opDollar on dlang.org.

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrej.mitrovich@gmail.com
           See Also|                            |http://d.puremagic.com/issu
                   |                            |es/show_bug.cgi?id=3474


--- Comment #1 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-02-04 14:14:17 PST ---
The feature was implemented in Issue3474 by https://github.com/D-Programming-Language/dmd/pull/442

I suggest Don and/or Kenji get on this since they know exactly how opDollar works. Apparently it can be a template, but I know very little about this.

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hsteoh@quickfur.ath.cx changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hsteoh@quickfur.ath.cx


--- Comment #2 from hsteoh@quickfur.ath.cx 2013-02-28 20:12:58 PST ---
I've used opDollar in some of my code; it appears to work like this:

obj[$] gets lowered to obj.opIndex(obj.opDollar!0);
obj[1,$] gets lowered to obj.opIndex(1, obj.opDollar!1);
obj[1,2,$] gets lowered to obj.opIndex(1, 2, obj.opDollar!2);

and so on. The $ is recognized in subexpressions as well, so:

obj[1, func(2,$), 3] gets lowered to obj.opIndex(1, func(2, obj.opDollar!1),
3).

In other words, the compile-time argument of opDollar is the index of position it appears in, in the arguments of the indexing operator.

Unfortunately, it appears that only opDollar!0 is implemented for opSlice (besides, slicing syntax currently does not support multiple ranges).

<aside>
But even with the current opIndex and opDollar, one can hack around the lack of
multidimensional opSlice by defining a custom range type, say: struct Range {
int start,end; }, then you can overload opIndex to recognize pseudo-slicing
syntax:

obj[Range(1,2), Range(2,$)] gets translated to obj.opIndex(Range(1,2),
Range(2,obj.opDollar!1)), so you just have to define: auto opIndex(Range r1,
Range r2), and you can have pseudo-multidimensional slicing. One can even use
variadic parameters to handle a mix of slicing and indexing:

auto opIndex(R...)(R args) {
    foreach (arg; args) {
        static if (typeof(arg) : Range) {
            // slice this dimension
        } else if (typeof(arg) : indexType) {
            // index this dimension
        }
    }
}

The $'s are correctly translated to opDollar!i based on their position i in the
[] operator, so this will correctly handle things like obj[$-1, Range(0,$-1)],
obj[Range(0,$), 10], etc..
</aside>

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hsteoh@quickfur.ath.cx changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #3 from hsteoh@quickfur.ath.cx 2013-03-02 13:05:22 PST ---
https://github.com/D-Programming-Language/d-programming-language.org/pull/292

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--- Comment #4 from github-bugzilla@puremagic.com 2013-10-26 06:55:56 PDT ---
Commit pushed to master at https://github.com/D-Programming-Language/dlang.org

https://github.com/D-Programming-Language/dlang.org/commit/2b6ff78b3d5148f9a3a9968fc1437a2a73d4fc45 Merge pull request #292 from quickfur/opdollar

Document opDollar (issue 7520)

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Kenji Hara <k.hara.pg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


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