Promote a lens to apply to each element of a list

Create a new lens that views and sets each element of the list.

map_l(l)

Arguments

l	the lens to promote

Details

Uses lapply under the hood for view and mapply under the hood for set. This means that set can be given a list of values to set, one for each element. If the input or update are lists this lens always returns a list. If the input and update are vectors this lens will return a vector.

Examples

(ex <- replicate(10, sample(1:5), simplify = FALSE))
#> [[1]]
#> [1] 1 4 2 5 3
#> 
#> [[2]]
#> [1] 3 2 1 4 5
#> 
#> [[3]]
#> [1] 5 1 4 3 2
#> 
#> [[4]]
#> [1] 1 2 5 3 4
#> 
#> [[5]]
#> [1] 2 3 4 1 5
#> 
#> [[6]]
#> [1] 4 1 2 3 5
#> 
#> [[7]]
#> [1] 1 5 4 2 3
#> 
#> [[8]]
#> [1] 3 5 4 1 2
#> 
#> [[9]]
#> [1] 4 2 5 3 1
#> 
#> [[10]]
#> [1] 4 5 3 2 1
#> 
view(ex, map_l(index(1)))
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [1] 3
#> 
#> [[3]]
#> [1] 5
#> 
#> [[4]]
#> [1] 1
#> 
#> [[5]]
#> [1] 2
#> 
#> [[6]]
#> [1] 4
#> 
#> [[7]]
#> [1] 1
#> 
#> [[8]]
#> [1] 3
#> 
#> [[9]]
#> [1] 4
#> 
#> [[10]]
#> [1] 4
#> 
set(ex, map_l(index(1)), 11:20)
#> [[1]]
#> [1] 11  4  2  5  3
#> 
#> [[2]]
#> [1] 12  2  1  4  5
#> 
#> [[3]]
#> [1] 13  1  4  3  2
#> 
#> [[4]]
#> [1] 14  2  5  3  4
#> 
#> [[5]]
#> [1] 15  3  4  1  5
#> 
#> [[6]]
#> [1] 16  1  2  3  5
#> 
#> [[7]]
#> [1] 17  5  4  2  3
#> 
#> [[8]]
#> [1] 18  5  4  1  2
#> 
#> [[9]]
#> [1] 19  2  5  3  1
#> 
#> [[10]]
#> [1] 20  5  3  2  1
#>