R/ternary_operator.R

In bazar: Miscellaneous Basic Functions

#' @title 
#' If-Then-Else ternary operator
#' 
#' @description 
#' This is a C like ternary operator, the syntax being 
#' \code{condition \%?\% true \%:\% false}. 
#' 
#' @param condition
#' logical. A vector. 
#' 
#' @param true,false
#' Values to use for \code{TRUE} and \code{FALSE} values of \code{condition}. 
#' They must be either the same length as \code{condition}, or length \code{1}. 
#' 
#' @param lhs
#' Left-hand side of \code{\%:\%}, which should come from the result of a 
#' \code{\%?\%} call. 
#' 
#' @return 
#' If \code{length(x) > 1}, then \code{\link{ifelse}} is used.  
#' 
#' @author Richie Cotton, see \url{https://stackoverflow.com/a/8791496/3902976}; 
#' Paul Poncet for the small modifications introduced.  
#' 
#' @export
#' @rdname ternary_operation
#' 
#' @examples 
#' (capitalize <- sample(c(TRUE, FALSE), 1))
#' capitalize %?% LETTERS[1:3] %:% letters[1:2]
#' 
#' # Does not work
#' \dontrun{
#' capitalize %?% 1*1:3 %:% 1:2
#' }
#' 
#' # Does work
#' capitalize %?% {1*1:3} %:% 1:2
#' 
#' # Does work too
#' capitalize %?% (1*1:3) %:% 1:2
#' 
#' # Vectorized version also works
#' c(capitalize,!capitalize) %?% "A" %:% c("b","c")
#' 
#' # Chaining operators is permitted 
#' FALSE %?% "a" %:% 
#'   (FALSE %?% "b") %:% 
#'   (capitalize %?% "C") %:% "c" 
#' 
"%?%" <- 
function(condition, 
         true) 
{
  list(condition = condition, 
       true = true)
}


#' @export
#' @rdname ternary_operation
#' 
"%:%" <- 
function(lhs, 
         false) 
{
  if (length(lhs$condition) == 1L) {
    if (lhs$condition) lhs$true else false
  } else {
    ifelse(lhs$condition, lhs$true, false)
  }
}