Is there a R function to find the next position of an element in a list

Question

I want to create a function that returns the next day

Here is what I got:

next_day <- function(day){
 + week = list('monday','tuesday','wednesday','thursday','friday','saturday','sunday')
 + pos <- index(day, week)
 + if(day=='sunday') return('monday')
 + if match(day,week) return week[pos+1]

Error: unexpected symbol in:
"   + if(day=='sunday') return('monday')
    + if match"

Answer 1

nextday <- function(day){
  week <- list('monday','tuesday','wednesday','thursday','friday','saturday','sunday')
  day <- stringr::str_to_lower(day)
  index <- match(day, week)
  if(index == 7){
    index = 0
  }
  week[[index+1]]
}

nextday("sunday")

Output :

[1] "monday"