On Wednesday, 15 September 2021 at 20:32:12 UTC, eXodiquas wrote:
```d
[1,0,3,4,0,5]
.fold!((a, e) => e != 0 ? a[0] ~ e : a[1] ~ e)(cast(int[][])
[[],[]])
.flatten
.writeln
```
This should sort all non 0s into the `a[0]` array and all 0s
into the `a[1]` array. But it won't work because the `~` does
not return the whole array (which is probably better for most
of the cases). So the question, is there a way to do this kind
of append, but getting the whole array back as a result in std?
You need to use `~=` instead of `~` to mutate an existing array:
```d
import std;
void main()
{
[1, 0, 3, 4, 0, 5]
.fold!((a, e) {
e != 0 ? (a[0] ~= e) : (a[1] ~= e);
return a;
})(cast(int[][]) [[], []])
.joiner
.writeln;
}
```
Of course, a more idiomatic solution would be to use
`std.algorithm.partition`:
```d
import std;
void main()
{
auto arr = [1, 0, 3, 4, 0, 5];
arr.partition!(e => e != 0); // in-place
arr.writeln;
}
```
