#Implement a multiplication game. A while loop that gives the user two random numbers from 2 to 12 and asks the user to #multiply them. Only exit the loop after five correct answers.

total <- 0
while (TRUE) {
  if (!total %in% 0:4) {
    total <- 0L
  }
  n <- sample(c(2:12), 2)
  cat("What is the product of ", n[1], " and ", n[2], "?\n", sep = "")
  x <- as.integer(readline())
  if (x == prod(n)) {
    total <- total + 1L
    cat("Right!")
    if (total == 5) break
    cat(" You just need", 5 - total, "more answers.\n\n")
  } else {
    cat("Wrong\n")
  }
}

# if (!total %in% 0:4) {
    total <- 0L
  }#

不知道划线部分有何作用？去掉对整个程序运行并没有影响。