Allow to continue interrupted `map()`

[Maximilian Girlich]

For me the main advantage of a for loop over map() in an interactive context is that I can easily continue the for loop after an interruption. An example workflow I regularly have:

slow_function <- function(x) {
  if (x == 5) {
    stop("something went wrong")
  }
  
  x
}

to_process <- 1:10
results <- list()
for (i in to_process) {
  results[[i]] <- slow_function(i)
}
#> Error in slow_function(i): something went wrong

print(i)
#> [1] 5
# now fix `slow_function()`

slow_function <- function(x) {
  x
}

for (j in to_process[-(1:(i - 1))]) {
  results[[j]] <- slow_function(j)
}

print(results)
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [1] 2
#> 
#> [[3]]
#> [1] 3
#> 
#> [[4]]
#> [1] 4
#> 
#> [[5]]
#> [1] 5
#> 
#> [[6]]
#> [1] 6
#> 
#> [[7]]
#> [1] 7
#> 
#> [[8]]
#> [1] 8
#> 
#> [[9]]
#> [1] 9
#> 
#> [[10]]
#> [1] 10

^{Created on 2023-09-05 with reprex v2.0.2}