https://d.puremagic.com/issues/show_bug.cgi?id=11880

           Summary: Reserve the keyword "yield"
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2014-01-07 18:38:02 PST ---
I suggest to reserve the keyword "yield" for future usage (just like the keyword "macro", "cent", "ucent"). This will avoid backward compatibility problems with D code that uses variable names "yield" today.

See Issue 5660 for info on "yield".


Today code that uses "yield" should give an explicit error message like this:

test.d(2): Error: yield not implemented


And this should compile:

void main() {
    static assert(!__traits(compiles, { yield(int) foo() { yield 1; }}));
}

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Jacob Carlborg <doob@me.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |doob@me.com


--- Comment #1 from Jacob Carlborg <doob@me.com> 2014-01-07 23:35:19 PST ---
"yield" is already used for function names in core.Thread and core.Fiber.

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Vladimir Panteleev <thecybershadow@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |thecybershadow@gmail.com


--- Comment #2 from Vladimir Panteleev <thecybershadow@gmail.com> 2014-01-08 09:42:11 EET ---
As I understand, "yield" doesn't need to be a keyword - it can be implemented as a language construct. The only limitation is that coroutines need to be started explicitly (which I think this is a plus as it improves readability).

I suggest closing this as WONTFIX.

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--- Comment #3 from Vladimir Panteleev <thecybershadow@gmail.com> 2014-01-08 09:42:54 EET ---
s/language construct/library construct/

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Maxim Fomin <maxim@maxim-fomin.ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |maxim@maxim-fomin.ru
         Resolution|                            |WONTFIX


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--- Comment #4 from bearophile_hugs@eml.cc 2014-01-08 03:06:11 PST ---
(In reply to comment #2)

> As I understand, "yield" doesn't need to be a keyword - it can be implemented as a language construct.

Do you have an example usage syntax (and implementation)? And is it going in
Phobos?

What about Issue 5660 ?


> The only limitation is that coroutines need to be
> started explicitly (which I think this is a plus as it improves readability).

This is the syntax I suggested, I think it's readable. What's the more readable usage syntax that you suggest?


yield(int) foo() {
    yield 1;
    yield 2;
}
void main() {
    import std.stdio, std.algorithm;
    foo.map!(x => x).writeln;
}

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--- Comment #5 from Vladimir Panteleev <thecybershadow@gmail.com> 2014-01-11 14:39:01 EET ---
(In reply to comment #4)
> Do you have an example usage syntax (and implementation)?

You posted this 5 years ago: http://forum.dlang.org/post/g7uhp6$317g$1@digitalmars.com

There are other, similar implementations.

> And is it going in Phobos?

I don't know of any plans for that.

> What about Issue 5660 ?

The same arguments apply there too. I see people posted their own coroutine implementations there as well.

> This is the syntax I suggested, I think it's readable. What's the more readable usage syntax that you suggest?

My argument is that the cost of introducing a breaking change in the language is not justified for the sake of syntax sugar.

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