A quick C implementation for “which.first” (`head(which(x), 1)`

) and
“which.last” (`tail(which(x), 1)`

).

```
wf(x, use.names = TRUE)
wl(x, use.names = TRUE)
```

## Arguments

- x
[`logical`

]

Logical vector.

- use.names
[`logical(1)`

]

If `TRUE`

and `x`

is named, the result is also
named.

## Value

[`integer(1)`

| `integer(0)`

].
Returns the index of the first/last `TRUE`

value in `x`

or
an empty integer vector if none is found. NAs are ignored.

## Examples

```
wf(c(FALSE, TRUE))
#> [1] 2
wl(c(FALSE, FALSE))
#> integer(0)
wf(NA)
#> integer(0)
```