On Sunday, August 24, 2025 6:30:08 AM Mountain Daylight Time David T. Oxygen
via Digitalmars-d-learn wrote:
> On Sunday, 24 August 2025 at 08:35:57 UTC, Per Nordlöw wrote:
> > Which are the pros and cons of foreach vs static foreach on a
> > compile time tuple in D in terms of compiler performance and
> > resource usage? Does static foreach generate more ast
> > duplications?
>
> --
> Yes, it will make the compile-time longer, but usually you can
> ignore.
> If you don't have `static foreach(int i;0..99999999)`，you are no
> need to worry about it.
You misunderstood the question. He was asking whether the performance
between foreach and static foreach differs when what's being iterated over
is a compile-time construct which therefore must be iterated at compile
time. And in such a sitation, the performance should be identical (or so
close that you couldn't tell the difference).
On the other hand,
foreach(i; 0 .. 10_000)
{...}
and
static foreach(i; 0 .. 10_000)
{{...}}
are completely different from one another, because the foreach would iterate
at runtime, whereas the static foreach would iterate at compile time,
because the arguments to foreach are not compile-time arguments.
In contrast,
foreach(i; AliasSeq!(1, 2, 3, 4, 5))
{...}
static foreach(i; AliasSeq!(1, 2, 3, 4, 5))
{{...}}
would both run at compile time, because AliasSeq is a compile-time
construct and must be evaluated at compile time.
- Jonathan M Davis
