On Tuesday, 9 June 2015 at 00:48:34 UTC, rsw0x wrote:
On Tuesday, 9 June 2015 at 00:01:07 UTC, Idan Arye wrote:
On Monday, 8 June 2015 at 22:15:32 UTC, rsw0x wrote:
On Monday, 8 June 2015 at 20:02:11 UTC, Andrei Alexandrescu
wrote:
I'm trying to collect together motivating examples and to
figure out the semantics of the feature.
maybe not completely related, but I made a blog post on using
CTFE to unroll foreach at compiletime
https://rsw0x.github.io/post/switch-unrolling/
I find myself often writing recursive templates for
compile-time generation of constructs that could be done
cleaner with static foreach.
I also use this method alot, and sometimes encounter this
"bug": http://dpaste.dzfl.pl/16af3c5dad73
The break inside the `foreach` is breaking from the `foreach`,
not from the `switch`, so it continues to execute the
`default` clause.
This is not really a bug - `foreach` unrolling is more of a
loop unrolling optimization that we hijack, so it makes sense
`break` inside it will act like it's inside a regular
`foreach`. With `static foreach`, we might want `break`(and
`continue`) to operate on the containing, runtime control
structure.
I knew there was something I was forgetting in that short
example, thanks for the reminder.
Interestingly, the assembly generated with `break` and `break
label` with a label on the switch is exactly the same. I don't
have time right now to go review the spec, so I have no idea if
that's correct.
Why wouldn't they? If we neglect RAII(for simplicity), `break`
jumps to the first instruction after the `foreach`, and `break
label` with a label on the `switch` jumps to the first
instruction after the `switch`. Since there is nothing in the
`switch` after the `foreach`, the first instruction after the
`foreach` is also the first instruction after the `switch`, so
the command to jump to that instruction is the same, and the
assembly is the same.
