'Strategy' design pattern in R

dp_strategy.R

qsort <- function(inp, cfun) {
  if (length(inp) > 1) {
    cres <- cfun(inp, inp[[length(inp)]])
    c(qsort(inp[cres < 0], cfun), inp[cres == 0], qsort(inp[cres > 0], cfun))
  } else {
    inp
  }
}

users <- list(list(name = "John Doe", subscription = 0),
              list(name = "Jane Doe", subscription = 1),
              list(name = "John Dur", subscription = 1),
              list(name = "Sara Der", subscription = 1))

alphabetic_sort <- function(uvec, uref) {

  vec_names <- sapply(uvec, function(x) x$name)
  vec_subs <- sapply(uvec, function(x) x$subscription)
  
  equal_users <- vec_subs == uref$subscription & vec_names == uref$name
  earlier_users <- vec_subs > uref$subscription | (vec_subs == uref$subscription & vec_names < uref$name)
  later_users <- vec_subs < uref$subscription | (vec_subs == uref$subscription & vec_names > uref$name)
  
  (!equal_users) * ((-1 * earlier_users) + (1 * later_users))

}
                     
reverse_sort <- function(uvec, uref) {
    
  vec_names <- sapply(uvec, function(x) x$name)
  vec_subs <- sapply(uvec, function(x) x$subscription)
  
  equal_users <- vec_subs == uref$subscription & vec_names == uref$name
  earlier_users <- vec_subs > uref$subscription | (vec_subs == uref$subscription & vec_names > uref$name)
  later_users <- vec_subs < uref$subscription | (vec_subs == uref$subscription & vec_names < uref$name)
  
  (!equal_users) * ((-1 * earlier_users) + (1 * later_users))

}
                     
qsort(users, alphabetic_sort)
qsort(users, reverse_sort)

As discussed here:
https://www.mpj-analytics.co.uk/2019/09/04/design-patterns-r-strategy/

Inspired by:
http://mishadoff.com/blog/clojure-design-patterns/#episode-2-strategy