Problems creating nested data or better solution in R

I want to create create an extra column with positions in a data frame. My plan was to use the start and end column as the input of seq command and expected with as.list to get a nested data entry which I can afterwards just unnest. But this is giving me an error.
So as n example:

tibble(
  start=c(1,7),
  end=c(3,10),
  total=15,
  value=c(100,200)
)

My expected result would be something like this:

tibble(
  start=c(1,1,1,7,7,7,7),
  end=c(3,3,3,10,10,10,10),
  total=15,
  value=c(100,100,100,200,200,200,200),
  position=c(1,2,3,7,8,9,10)
)

I tried something like

tibble(
  start=c(1,7),
  end=c(3,10),
  total=15,
  value=c(100,200)
) %>% 
  mutate(position=as.list(seq(start,end))) %>% 
  unnest(position)

What am I doing wrong?

>Solution :

The error comes from seq. You must apply your function row-wise, since the call is interpreting seq(c(1, 7), c(3, 10)) by default.

To do that, you can use mapply, pmap, or rowwise.

tbl %>% 
  mutate(position = mapply(seq, start, end))

tbl %>% 
  rowwise() %>% 
  mutate(position = list(seq(start, end)))