Re:C++20 Improved the For-Loop Syntax
by WalterBright on Tuesday July 14, 2026 @09:35PM
(#48915184)
C++ should copy D's elegance:
[ Parent
| on HN ]
Go is similar:
package main
import "fmt"
var vec = []string{"the", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"}
func main() {
for i, s := range vec {
fmt.Printf("%d: %s\n", i, s)
}
}
Using `fmt.Println(i, ":", s)` inserts spaces on both sides of the colon, so the output is not quite right.I find Go's `range` syntax easier to read than D's `(i, s; vec)` -- although generator functions that work with `range` have unaesthetic return types.
Re:C++20 Improved the For-Loop Syntax
by WalterBright on Tuesday July 14, 2026 @10:29PM
(#48915550)
D has several usages for `foreach` depending on the number and type of its arguments. In this case, it sees that `vec` is an array, and so constructs a loop over the array. If `vec` was a range, the loop will be constructed as a loop over the array.
It's nice because it makes the syntax for arrays and ranges interchangeable, making for easy refactoring.
Go is similar: `for/range` has always worked on arrays, slices, maps, strings and channels, and they extended it to integers in version 1.22 and to user-defined generators in version 1.23. It generates one or two outputs depending on the type of the RHS, but one can assign the index value to _ to ignore it. Among standard types, only channels and integers generate one output; containers (including strings) give an index or key and a value.
I find Go’s version worse in that it does not allow you to elide the index (which is not needed most of the time). You have to write `for _, s := range vec`, as `for s := range vec` makes s the index.
Re:C++20 Improved the For-Loop Syntax
by WalterBright on Wednesday July 15, 2026 @01:39PM
(#48924429)
To clarify,
foreach (s; vec)
works if you don't need the index. To be able to modify s in place: foreach (ref s; vec) s = "replacement";I was talking about Go. I know you don’t need the index in D.
Re:C++20 Improved the For-Loop Syntax
by WalterBright on Tuesday July 14, 2026 @09:47PM
(#48915272)
Although D is a strongly typed language, it is very good at type inference. The `s` is inferred as `string`, and `i` as `size_t`.
I don't like that semi-colon. AFAICT `i, s;` is not an independent statement. `i, s: vec` would have been fine, but `;` ?!?! madness.
Well, others might have said `i, s:` is not an independent label.
C++23 example,
import std;
using namespace std;
int main() {
vector vec = {
"the", "quick", "brown", "fox",
"jumped", "over", "the", "lazy", "dog"
};
for (auto&& [i, it] : vec | std::views::enumerate)
println ("{}:{}", ++i, it);
}
As I keep mentioning, the features being copied, slowly erode D's relevance.
Re:C++20 Improved the For-Loop Syntax
by WalterBright on Wednesday July 15, 2026 @01:37PM
(#48924383)
If you prefer writing:
for (auto&& [i, it] : vec | std::views::enumerate)
println ("{}:{}", ++i, it);
instead of: foreach (i, s; vec)
writeln(i, ": ", s);
well, what can I say?We may first need to go over what "elegant" means I guess. :)
There is elegant when writing code by hand, and when reviewing code by AI agents.