On Monday, 5 February 2024 at 14:26:45 UTC, Basile B. wrote:
On Tuesday, 30 January 2024 at 15:38:26 UTC, Paul Backus wrote:
[...]
This definitely isn't allowed in C or C++. I wonder what the
rationale is for having this behavior in D?
[1]: https://dlang.org/spec/expression.html
An hypothesis is that this makes codegening the pre and the
post variants almost identical. The only difference is what is
yield.
[Proof](https://gitlab.com/styx-lang/styx/-/blob/master/src/styx/backend/irgen.sx?ref_type=heads#L3383).
Now there's not much to say about the topic, I just thought it
was amusing to share that (user1234 is my noname nickname here)
as people might not realize how much certain expressions allows.
In the same vein you have the possibility to select an lvalue
with a conditional expression. Pretty sure nobody knows that
the following is legal
```d
int a,b;
int c = rand();
((c & 3) ? a : b) = 42;
```
BTW, "achtung off topic", that's pretty much how the optional
access can be an lvalue:
```d
struct S {int a};
S* s; // null, by default init
s?.a = 0; // no access violation !! + valgrind is happy
```
You can lower that to a conditional expression:
```d
struct S {int a};
S* s;
typeof(S.a) __fallback; // compiler-generated
(s ? s.a : __fallback) = 0;
```
I've played a lot with that kind of expressions during the two
last years. They're funny but apparently not good enough for D ;)
To conclude.
