js-ternary-in-r.R

`?` <- function(condition, result) {
  if (missing(result)) return(
    utils::`?`(deparse(substitute(condition)))
  )
  result <- substitute(result)
  if (!is.call(result) || !identical(result[[1]], as.symbol(':'))) {
    stop("Invalid syntax. Expected <condition> ? <if_true> : <if_false>", call. = FALSE)
  }
  eval(call("if", condition, result[[2]], result[[3]]))
}

TRUE ? "yes" : "no"
#> [1] "yes"
FALSE ? "yes" : "no"
#> [1] "no"
TRUE ? (1:3) : (4:6)
#> [1] 1 2 3
FALSE ? (1:3) : (4:6)
#> [1] 4 5 6
TRUE ? "yes"
#> Error: Invalid syntax. Expected <condition> ? <if_true> : <if_false>

maybe <- function() as.logical(sample(0:1, 1))
message(
  "The dog ", maybe() ? "did" : "didn't", " eat my homework."
)
#> The dog did eat my homework.

# And help still (mostly) works
?runif

# https://git.io/JIP0C

# thanks @jimhester
# https://gist.github.com/jimhester/3ef5b148e03999a7b5124f93b0c1f404