# Description
The correction made here concerns the issue #8431. Indeed, the algorithm
initially proposed to remove elements of a `vector` performed a loop
with `remove` and an incident therefore appeared when several values
were equal because the deletion was done outside the length of the
vector:
```rust
let mut found = false;
for (i, col) in cols.clone().iter().enumerate() {
if col == col_name {
cols.remove(i);
vals.remove(i);
found = true;
}
}
```
Then, `[[a, a]; [1, 2]] | reject a: ` gave `thread 'main' panicked at
'removal index (is 1) should be < len (is 1)',
crates/nu-protocol/src/value/mod.rs:1213:54`.
The proposed correction is therefore the implementation of the
`retain_mut` utility dedicated to this functionality.
```rust
let mut found = false;
let mut index = 0;
cols.retain_mut(|col| {
if col == col_name {
found = true;
vals.remove(index);
false
} else {
index += 1;
true
}
});
```
0bd4d27e8d