[Assert] Argument checking function #R

assert.R

assert <- function(..., msg=NULL) {
  # Assert that each of the provided expression is true. Otherwise returns a
  # description of each failed assertion.
  # 
  # Args:
  #   ...: List of logical assertions
  #   msg: Optional parameter printed when one of the assertions fails.
  # 
  # Returns:
  #   Nothing if all assertions pass. Otherwise throws an error describing which
  #   assertions failed.
  #   
  # Examples:
  # > assert(2 < 1, 1 == 1, "1" == 2)
  # ## Error in assert(2 < 1, 1 == 1, "1" == 2) : Failed checks: 
  # ##       2 < 1 
  # ##       "1" == 2 
  # 
  # # In a function to validate arguments:
  # > sum <- function(a, b) {
  # >   assert(is.numeric(a),
  # >          is.numeric(b),
  # >          length(a) == length(b))
  # >   return(a+b)
  # > }
  # > sum("1", 2)
  # ## Error: in sum(a = "1", b = c(1, 2))
  # ## Failed checks: 
  # ##        is.numeric(a) 
  # ##        length(a) == length(b) 
  # 

  r = c(...)
  if (any(!r)) {
    fails = paste0(substitute(c(...)))[-1][!r]
    if(identical(parent.frame(), globalenv())) {
      stop(c("Failed checks: \n\t", 
            paste(fails, "\n\t"),
            "\n", msg))
    } else {
      msg = c("in ",
              eval(quote(match.call()), parent.frame()),
              "\n",
              "Failed checks: \n\t", 
              paste(fails, "\n\t"),
              "\n", msg)
      stop(msg, call. = FALSE)
    }
  }
}

assert_example.R

sum <- function(a, b) {
	assert(is.numeric(a), is.numeric(b))
	assert(length(a) == length(b))
  
	return(a+b)
}

sum("1", c(1,2))