Re: [vim9script] Forward declarations for classes?

> Consider the following example:
>
> class Rgb
> this.r: float
> this.g: float
> this.b: float
>
> def ToHsv(): Hsv
> # ...
> enddef
> endclass
>
> class Hsv
> this.h: float
> this.s: float
> this.v: float
>
> def ToRgb(): Rgb
> # ...
> enddef
> endclass
>
> In a scenario like the above, the return type of ToHsv() must be changed
> to `any`. Is a mechanism to make the above code legal being considered?
>
> Of a similar flavour:
>
> class X
> def Clone(): X
> # Return a copy of this
> enddef
> endclass
>
> Currently, Clone() must be typed as `any`.

The second one should just work. Currently the class is only defined
when "endclass" is found. Doing it earlier is more implementation work,
but it should not require anything on the user side.

For the first example I'm not sure what the best solution is. There is
a plan to add some kind of typedef, but it would still require something
extra to indicate the actual implementation will follow later.

There is trouble when it's not just the class name that needs to be
known, but also what it contains. Then a forward declaration quickly
becomes a lot of duplicate text. And recursive dependencies need to be
handled, which is also relevant in this example.


--
ARTHUR: Will you ask your master if he wants to join my court at Camelot?!
GUARD #1: But then of course African swallows are not migratory.
GUARD #2: Oh, yeah...
GUARD #1: So they couldn't bring a coconut back anyway...
The Quest for the Holy Grail (Monty Python)

/// Bram Moolenaar -- Bram@Moolenaar.net -- http://www.Moolenaar.net \\\
/// \\\
\\\ sponsor Vim, vote for features -- http://www.Vim.org/sponsor/ ///
\\\ help me help AIDS victims -- http://ICCF-Holland.org ///

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/vim_use/20230326202817.7BA141C128A%40moolenaar.net.